{"id":12314,"date":"2026-02-26T08:36:02","date_gmt":"2026-02-26T08:36:02","guid":{"rendered":"https:\/\/hlh-js.com\/?p=12314"},"modified":"2026-03-09T07:11:51","modified_gmt":"2026-03-09T07:11:51","slug":"how-plastic-media-is-used-in-aerospace-depainting","status":"publish","type":"post","link":"https:\/\/hlh-js.com\/ru\/resource\/\u0431\u043b\u043e\u0433\/how-plastic-media-is-used-in-aerospace-depainting\/","title":{"rendered":"How Plastic Media Is Used in Aerospace Depainting"},"content":{"rendered":"<!-- ============================================================\n     CLUSTER ARTICLE #6 \u2014 WordPress Post Content\n     Title: How Plastic Media Is Used in Aerospace Depainting\n     \u7c98\u8d34\u65b9\u5f0f\uff1aGutenberg\u300c\u81ea\u5b9a\u4e49 HTML\u300d\u5757 \u6216 \u7ecf\u5178\u7f16\u8f91\u5668\u300c\u6587\u672c\u300d\u6a21\u5f0f\n     ============================================================ -->\n\n<style>\n\/* \u2500\u2500 .pm- \u524d\u7f00\u6837\u5f0f\uff08\u7cfb\u5217\u6587\u7ae0\u5171\u7528\uff0c\u6df1\u84dd\u519b\u673a\u4e3b\u9898\uff09 \u2500\u2500 *\/\n.pm-toc{background:#f0f4ff;border:1px solid #c7d2fe;border-left:4px solid #1e3a8a;padding:24px 28px;margin:0 0 40px;border-radius:4px}\n.pm-toc-title{font-size:13px;font-weight:700;text-transform:uppercase;letter-spacing:.1em;color:#64748b;margin:0 0 14px}\n.pm-toc ol{margin:0;padding-left:20px}\n.pm-toc li{margin:6px 0;font-size:15px}\n.pm-toc li a{color:#1e3a8a;text-decoration:none}\n.pm-toc li a:hover{text-decoration:underline}\n.pm-toc ol ol{margin-top:4px;padding-left:18px}\n.pm-toc ol ol li{font-size:13.5px;margin:4px 0}\n\n.pm-callout{background:#f0f4ff;border:1px solid #c7d2fe;border-left:4px solid #1e3a8a;padding:16px 20px;margin:24px 0;border-radius:0 4px 4px 0;font-size:15px;line-height:1.65}\n.pm-callout strong{color:#1e3a8a}\n.pm-callout-green{background:#f0fdf4;border-color:#bbf7d0;border-left-color:#16a34a}\n.pm-callout-green strong{color:#15803d}\n.pm-callout-warn{background:#fffbeb;border-color:#fde68a;border-left-color:#d97706}\n.pm-callout-warn strong{color:#92400e}\n.pm-callout-danger{background:#fef2f2;border-color:#fecaca;border-left-color:#dc2626}\n.pm-callout-danger strong{color:#991b1b}\n.pm-callout-orange{background:#fff7ed;border-color:#fed7aa;border-left-color:#ea580c}\n.pm-callout-orange strong{color:#c2410c}\n\n.pm-table-wrap{overflow-x:auto;margin:24px 0;border:1px solid #e2e8f0;border-radius:6px}\n.pm-table-wrap table{width:100%;border-collapse:collapse;font-size:14px;min-width:500px}\n.pm-table-wrap thead tr{background:#f1f5f9}\n.pm-table-wrap th{font-size:11.5px;font-weight:700;text-transform:uppercase;letter-spacing:.1em;color:#475569;padding:12px 14px;text-align:left;border-bottom:1px solid #e2e8f0;white-space:nowrap}\n.pm-table-wrap td{padding:11px 14px;border-bottom:1px solid #f1f5f9;vertical-align:top;color:#374151;font-size:14px}\n.pm-table-wrap tbody tr:last-child td{border-bottom:none}\n.pm-table-wrap tbody tr:hover{background:#fafafa}\n.pm-table-wrap td:first-child{font-weight:600;color:#111827}\n\n.pm-badge{display:inline-block;font-size:11px;font-weight:600;padding:2px 8px;border-radius:20px;letter-spacing:.04em}\n.pm-badge-high{background:#dcfce7;color:#166534}\n.pm-badge-med{background:#fef9c3;color:#854d0e}\n.pm-badge-low{background:#fee2e2;color:#991b1b}\n.pm-badge-blue{background:#dbeafe;color:#1e40af}\n.pm-badge-navy{background:#e0e7ff;color:#1e3a8a}\n.pm-badge-gray{background:#f1f5f9;color:#475569}\n.pm-badge-orange{background:#ffedd5;color:#c2410c}\n\n\/* Aircraft zone diagram *\/\n.pm-aircraft-zones{margin:28px 0}\n.pm-zone-row{display:grid;grid-template-columns:200px 1fr;gap:0;border-bottom:1px solid #f1f5f9;align-items:stretch}\n.pm-zone-row:first-child{border-top:1px solid #e2e8f0;border-radius:6px 6px 0 0;overflow:hidden}\n.pm-zone-row:last-child{border-radius:0 0 6px 6px;border-bottom:1px solid #e2e8f0;overflow:hidden}\n.pm-zone-label{background:#1e3a8a;color:#fff;padding:14px 16px;font-size:13px;font-weight:700;display:flex;align-items:center;gap:8px;flex-shrink:0}\n.pm-zone-label .zone-icon{font-size:18px;flex-shrink:0}\n.pm-zone-detail{padding:14px 16px;background:#f8fafc;font-size:13.5px;color:#374151;line-height:1.6;display:flex;align-items:center;gap:20px;flex-wrap:wrap}\n.pm-zone-detail .zd-media{font-weight:700;color:#1e3a8a;white-space:nowrap;flex-shrink:0}\n.pm-zone-detail .zd-note{color:#64748b;font-size:13px}\n\n\/* Military vs commercial *\/\n.pm-sector-grid{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin:24px 0}\n.pm-sector-card{border:1px solid #e2e8f0;border-radius:8px;overflow:hidden}\n.pm-sector-head{padding:16px 18px;font-weight:700;font-size:14px;color:#fff}\n.pm-sector-head.mil{background:#1e3a8a}\n.pm-sector-head.civil{background:#0369a1}\n.pm-sector-head .sh-sub{font-size:11px;font-weight:400;opacity:.85;margin-top:3px}\n.pm-sector-body{padding:16px 18px;background:#f8fafc}\n.pm-sector-body ul{margin:0;padding-left:18px}\n.pm-sector-body ul li{font-size:13.5px;color:#374151;margin:6px 0;line-height:1.5}\n\n\/* Coating system layers *\/\n.pm-coating-stack{margin:24px 0;border:1px solid #e2e8f0;border-radius:8px;overflow:hidden}\n.pm-coating-layer{display:flex;align-items:center;gap:16px;padding:12px 18px;border-bottom:1px solid #f1f5f9}\n.pm-coating-layer:last-child{border-bottom:none}\n.pm-coating-layer .cl-num{width:28px;height:28px;border-radius:4px;display:flex;align-items:center;justify-content:center;font-size:12px;font-weight:700;color:#fff;flex-shrink:0}\n.pm-coating-layer .cl-name{font-size:14px;font-weight:700;color:#111827;min-width:180px;flex-shrink:0}\n.pm-coating-layer .cl-spec{font-size:13px;color:#64748b;flex:1}\n.pm-coating-layer .cl-thick{font-size:12px;font-weight:600;color:#1e3a8a;white-space:nowrap}\n\n\/* Process compliance timeline *\/\n.pm-compliance-flow{margin:28px 0;display:flex;flex-direction:column;gap:0}\n.pm-cf-step{display:flex;gap:0;align-items:stretch}\n.pm-cf-step:last-child .pm-cf-line{display:none}\n.pm-cf-left{display:flex;flex-direction:column;align-items:center;width:48px;flex-shrink:0}\n.pm-cf-dot{width:36px;height:36px;background:#1e3a8a;border-radius:6px;display:flex;align-items:center;justify-content:center;color:#fff;font-size:12px;font-weight:700;flex-shrink:0;margin-top:2px}\n.pm-cf-line{width:2px;flex:1;background:#c7d2fe;min-height:20px;margin:4px 0}\n.pm-cf-body{padding:2px 0 28px 16px;flex:1}\n.pm-cf-body h4{font-size:15px;font-weight:700;color:#111827;margin:0 0 6px}\n.pm-cf-body p{font-size:14px;color:#4b5563;margin:0 0 6px;line-height:1.7}\n.pm-cf-body .cf-doc{display:inline-flex;align-items:center;gap:6px;background:#e0e7ff;color:#1e3a8a;font-size:12px;font-weight:600;padding:3px 10px;border-radius:4px;margin-top:4px}\n.pm-cf-body .cf-tip{font-size:13px;color:#64748b;font-style:italic;margin-top:6px}\n\n\/* Parameter display \u2014 navy *\/\n.pm-param-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(148px,1fr));gap:12px;margin:24px 0}\n.pm-param-card{background:#f0f4ff;border:1px solid #c7d2fe;border-radius:6px;padding:16px;text-align:center}\n.pm-param-value{font-size:26px;font-weight:900;color:#1e3a8a;line-height:1;margin-bottom:4px}\n.pm-param-unit{font-size:11px;color:#3730a3;font-weight:600;text-transform:uppercase;letter-spacing:.08em}\n.pm-param-label{font-size:12px;color:#6b7280;margin-top:6px;line-height:1.4}\n\n\/* Alloy compatibility cards *\/\n.pm-alloy-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(185px,1fr));gap:12px;margin:24px 0}\n.pm-alloy-card{border:1px solid #e2e8f0;border-radius:6px;overflow:hidden}\n.pm-alloy-head{padding:10px 14px;font-size:13px;font-weight:700}\n.pm-alloy-head.primary{background:#dcfce7;color:#166534}\n.pm-alloy-head.secondary{background:#dbeafe;color:#1e40af}\n.pm-alloy-head.caution{background:#fef9c3;color:#854d0e}\n.pm-alloy-head.special{background:#f3e8ff;color:#6b21a8}\n.pm-alloy-body{padding:10px 14px;background:#f8fafc;font-size:12.5px;color:#4b5563;line-height:1.6}\n\n\/* Documentation matrix *\/\n.pm-doc-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(210px,1fr));gap:14px;margin:24px 0}\n.pm-doc-card{background:#f8fafc;border:1px solid #e2e8f0;border-radius:6px;padding:16px 18px}\n.pm-doc-card .dc-icon{font-size:22px;margin-bottom:8px}\n.pm-doc-card h4{font-size:14px;font-weight:700;color:#1e3a8a;margin:0 0 6px}\n.pm-doc-card p{font-size:13px;color:#4b5563;margin:0;line-height:1.55}\n\n\/* Chemical comparison banner *\/\n.pm-chem-compare{display:grid;grid-template-columns:1fr 1fr;gap:0;margin:28px 0;border:1px solid #e2e8f0;border-radius:8px;overflow:hidden}\n.pm-chem-col{padding:0}\n.pm-chem-head{padding:14px 18px;font-weight:700;font-size:13px;color:#fff}\n.pm-chem-head.plastic{background:#1e3a8a}\n.pm-chem-head.chemical{background:#6b7280}\n.pm-chem-body{padding:14px 18px;background:#f8fafc;border-right:1px solid #e2e8f0}\n.pm-chem-body:last-child{border-right:none}\n.pm-chem-body ul{margin:0;padding-left:16px}\n.pm-chem-body ul li{font-size:13px;color:#374151;margin:6px 0;line-height:1.5}\n\n\/* FAQ *\/\n.pm-faq{margin:0}\n.pm-faq-item{border-bottom:1px solid #f1f5f9;padding:18px 0}\n.pm-faq-item:last-child{border-bottom:none}\n.pm-faq-q{font-size:16px;font-weight:700;color:#111827;margin:0 0 8px}\n.pm-faq-a{font-size:15px;color:#4b5563;margin:0;line-height:1.7}\n\n\/* Cluster links *\/\n.pm-cluster-group{margin:0 0 24px}\n.pm-cluster-label{font-size:11px;font-weight:700;text-transform:uppercase;letter-spacing:.12em;color:#94a3b8;margin:0 0 10px}\n.pm-cluster-group ul{list-style:none;padding:0;margin:0;display:flex;flex-direction:column;gap:4px}\n.pm-cluster-group ul li a{display:flex;align-items:center;gap:8px;color:#1e3a8a;text-decoration:none;font-size:14.5px;padding:8px 12px;border:1px solid #e2e8f0;border-radius:4px;background:#fafafa}\n.pm-cluster-group ul li a:hover{background:#f0f4ff;border-color:#c7d2fe}\n.pm-cluster-group ul li a::before{content:\"\u2192\";color:#1e3a8a;font-weight:700;flex-shrink:0}\n\n.pm-section-divider{border:none;border-top:1px solid #f1f5f9;margin:48px 0}\n\n@media(max-width:680px){\n  .pm-sector-grid{grid-template-columns:1fr}\n  .pm-chem-compare{grid-template-columns:1fr}\n  .pm-zone-row{grid-template-columns:1fr}\n  .pm-zone-label{border-radius:0}\n}\n@media(max-width:480px){\n  .pm-param-grid{grid-template-columns:repeat(2,1fr)}\n  .pm-alloy-grid{grid-template-columns:1fr 1fr}\n  .pm-doc-grid{grid-template-columns:1fr}\n  .pm-coating-layer{flex-direction:column;gap:6px}\n  .pm-coating-layer .cl-name{min-width:unset}\n}\n<\/style>\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     INTRO\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h1>How Plastic Media Is Used in Aerospace Depainting<\/h1>\n<p>Every commercial airliner is stripped to bare metal and completely repainted on a cycle of roughly five to seven years. Military aircraft are stripped and repainted on even tighter schedules \u2014 some tactical aircraft every two to three years depending on operational tempo and environmental exposure. Multiply that across a fleet of hundreds or thousands of airframes, and aerospace depainting becomes one of the largest-volume, most technically demanding surface preparation operations in any industry.<\/p>\n\n<p>For most of the twentieth century, the method of choice was chemical stripping: applying highly caustic alkaline or solvent-based strippers to the aircraft skin, waiting hours for the coating to soften, and removing the result with high-pressure water blast. The process worked, but it generated enormous volumes of hazardous chemical waste, required extensive neutralization of the stripped surfaces, and was progressively falling out of regulatory favor as environmental controls tightened.<\/p>\n\n<p>Plastic media blasting \u2014 the use of engineered polymer abrasive particles propelled by compressed air \u2014 emerged as the primary replacement for chemical stripping in aerospace depainting starting in the 1980s, driven by U.S. Air Force programs seeking to reduce solvent and hazardous waste generation in depot maintenance operations. Today, plastic media blasting is the dominant depaint method for military aircraft globally and is increasingly specified for commercial airline maintenance. This guide explains why, how the process works, and what the technical requirements are for qualified aerospace depainting operations.<\/p>\n\n<p>For a foundational overview of plastic media types, see: <a href=\"https:\/\/hlh-js.com\/resource\/blog\/what-is-plastic-media-the-complete-guide-to-types-uses-applications\/\">What Is Plastic Media? The Complete Guide<\/a>.<\/p>\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     TABLE OF CONTENTS\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<nav class=\"pm-toc\" aria-label=\"Table of Contents\">\n  <p class=\"pm-toc-title\">\ud83d\udccb Table of Contents<\/p>\n  <ol>\n    <li><a href=\"#aero-why\">Why Aerospace Depainting Requires a Specialized Approach<\/a><\/li>\n    <li><a href=\"#aero-history\">The History: From Chemical Strip to Plastic Media<\/a><\/li>\n    <li><a href=\"#aero-milspec\">MIL-P-85891A: The Standard That Governs It All<\/a><\/li>\n    <li><a href=\"#aero-coating-systems\">Aerospace Coating Systems Being Removed<\/a><\/li>\n    <li><a href=\"#aero-substrates\">Aircraft Substrate Alloys &amp; Media Compatibility<\/a><\/li>\n    <li><a href=\"#aero-zones\">Zone-by-Zone: Different Areas, Different Requirements<\/a><\/li>\n    <li><a href=\"#aero-military\">Military Aircraft Depainting<\/a><\/li>\n    <li><a href=\"#aero-commercial\">Commercial Airline Heavy Maintenance<\/a><\/li>\n    <li><a href=\"#aero-composite\">Composite Structure Depainting<\/a><\/li>\n    <li><a href=\"#aero-parameters\">Qualified Blast Parameters<\/a><\/li>\n    <li><a href=\"#aero-process\">The Qualified Depaint Process: Step by Step<\/a><\/li>\n    <li><a href=\"#aero-vs-chemical\">Plastic Media vs Chemical Stripping: Full Comparison<\/a><\/li>\n    <li><a href=\"#aero-fatigue\">Fatigue Life Considerations<\/a><\/li>\n    <li><a href=\"#aero-docs\">Documentation &amp; Traceability Requirements<\/a><\/li>\n    <li><a href=\"#aero-waste\">Waste Management &amp; Environmental Compliance<\/a><\/li>\n    <li><a href=\"#aero-faq\">\u0427\u0430\u0441\u0442\u043e \u0437\u0430\u0434\u0430\u0432\u0430\u0435\u043c\u044b\u0435 \u0432\u043e\u043f\u0440\u043e\u0441\u044b<\/a><\/li>\n    <li><a href=\"#aero-related\">Related Guides<\/a><\/li>\n  <\/ol>\n<\/nav>\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 1 \u2014 WHY SPECIALIZED\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-why\">Why Aerospace Depainting Requires a Specialized Approach<\/h2>\n\n<p>Stripping paint from an aircraft is categorically different from stripping paint from an automobile or an industrial component. The governing constraints in aerospace depainting are not primarily about efficiency or convenience \u2014 they are about structural integrity, fatigue life, and airworthiness certification. Every decision about media type, blast parameters, and process sequence is made against the backdrop of a fundamental regulatory requirement: the aircraft must emerge from the depaint process in a condition that is aeronautically safe and certifiably airworthy.<\/p>\n\n<p>Three structural realities define why aerospace depainting demands this level of rigor:<\/p>\n\n<p><strong>Aluminum alloy fatigue sensitivity.<\/strong> Aircraft aluminum alloys \u2014 particularly the 2000-series and 7000-series high-strength alloys used for primary structure \u2014 are fatigue-sensitive materials. Their fatigue life (the number of load cycles they can endure before initiating a crack) is directly affected by the state of their surface. Any surface treatment process that introduces tensile residual stress, removes material beyond a micro-scale profile, or creates surface discontinuities reduces fatigue life. A properly controlled plastic media blast process introduces no net tensile residual stress and removes no measurable aluminum \u2014 but an improperly controlled process can do both, with consequences that may not manifest until the aircraft has accumulated thousands of additional flight hours.<\/p>\n\n<p><strong>Dimensional criticality.<\/strong> Aircraft skins, particularly on wing panels and pressurized fuselage sections, are manufactured to tight thickness tolerances. Processes that remove metal \u2014 like aggressive mineral abrasive blasting \u2014 can thin skins below their minimum acceptable gauge over multiple depaint cycles. Plastic media blasting, because it fractures at the metal surface rather than cutting into it, does not remove measurable quantities of metal from aluminum substrates at qualified parameters.<\/p>\n\n<p><strong>Chromate primer exposure and management.<\/strong> Most legacy military aircraft and many older commercial aircraft carry chromate-containing primers \u2014 specifically MIL-PRF-23377 zinc chromate or barium chromate primers \u2014 as their primary corrosion protection layer. These primers are highly effective corrosion inhibitors but contain hexavalent chromium, a regulated carcinogen. The depaint process that removes these coatings generates chromate-contaminated blast media waste and dust, which must be managed under strict environmental and occupational health regulations.<\/p>\n\n<div class=\"pm-callout\">\n  <strong>The bottom line:<\/strong> In aerospace depainting, the abrasive must be hard enough to remove a multi-layer MIL-SPEC coating system efficiently, yet soft enough to leave the aluminum alloy structure beneath it physically and metallurgically unchanged. Type II urea formaldehyde plastic blast media, operating within the parameters defined by MIL-P-85891A, is the material that satisfies both requirements simultaneously.\n<\/div>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 2 \u2014 HISTORY\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-history\">The History: From Chemical Strip to Plastic Media<\/h2>\n\n<p>The shift from chemical stripping to plastic media blasting in aerospace maintenance is one of the clearest examples of environmental regulation driving process innovation in industrial manufacturing.<\/p>\n\n<p>Through the 1970s, chemical stripping was the universal aerospace depaint method. The process involved applying methylene chloride-based paint strippers or high-pH alkaline strippers to the aircraft skin, typically using brushes or spray equipment inside a hangar. The stripper softened the coating layers, which were then removed with scrapers and high-pressure water. The resulting effluent \u2014 a mixture of water, caustic chemicals, dissolved paint, and chromate primer residue \u2014 was collected in floor drains and treated as industrial wastewater.<\/p>\n\n<p>By the early 1980s, tightening environmental regulations around methylene chloride (a probable human carcinogen) and hexavalent chromium in wastewater were making chemical stripping increasingly costly and difficult to operate in compliance. The U.S. Air Force, which operates the largest fleet maintenance operation in the world, began funding research into alternative depaint technologies that could replace chemical stripping without compromising maintenance quality or aircraft structural integrity.<\/p>\n\n<p>The result was the development and qualification of plastic media blasting under a series of Air Force programs culminating in the promulgation of MIL-P-85891A in 1989 \u2014 the military specification that defined the media types, test requirements, and process controls for plastic blast media in aircraft maintenance. By the mid-1990s, plastic media blasting had become the standard depaint method at Air Force and Navy depot maintenance facilities across the United States. The Marine Corps, Army, and allied military aviation organizations followed, and the technology progressively transferred into commercial airline heavy maintenance.<\/p>\n\n<p>Today, plastic media blasting is used to depaint aircraft ranging from single-engine trainers to wide-body commercial transports, across military, commercial, and general aviation contexts, with the MIL-P-85891A standard as the common technical foundation across all sectors.<\/p>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 3 \u2014 MIL-SPEC\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-milspec\">MIL-P-85891A: The Standard That Governs It All<\/h2>\n\n<p>MIL-P-85891A, <em>Plastic Media, Abrasive Blasting<\/em>, is the foundational document for aerospace plastic blast media. It was developed under the auspices of the U.S. Department of Defense to establish minimum performance requirements for plastic blast abrasives used in aircraft depaint and surface preparation operations. Understanding this standard is essential for anyone involved in aerospace depaint procurement, process engineering, or quality assurance.<\/p>\n\n<p>The standard defines five media types by resin chemistry:<\/p>\n\n<div class=\"pm-table-wrap\">\n  <table>\n    <thead>\n      <tr>\n        <th>\u0422\u0438\u043f<\/th>\n        <th>\u0421\u043c\u043e\u043b\u0430<\/th>\n        <th>\u0422\u0432\u0435\u0440\u0434\u043e\u0441\u0442\u044c \u043f\u043e \u041c\u043e\u043e\u0441\u0443<\/th>\n        <th>Primary Use in Aerospace<\/th>\n        <th>Availability<\/th>\n      <\/tr>\n    <\/thead>\n    <tbody>\n      <tr>\n        <td>Type I<\/td>\n        <td>Polyester<\/td>\n        <td>~2.5<\/td>\n        <td>Tumbling\/mass finishing; rarely blast<\/td>\n        <td>Limited suppliers<\/td>\n      <\/tr>\n      <tr>\n        <td>Type II<\/td>\n        <td>Urea Formaldehyde<\/td>\n        <td>~3.5<\/td>\n        <td><strong>Primary aerospace depaint media<\/strong>; aluminum structures, standard MIL-SPEC coatings<\/td>\n        <td>Widely available; most common<\/td>\n      <\/tr>\n      <tr>\n        <td>Type III<\/td>\n        <td>Melamine Formaldehyde<\/td>\n        <td>~4.0<\/td>\n        <td>Steel structures, titanium; harder coatings; less common in aerospace<\/td>\n        <td>Available; less common<\/td>\n      <\/tr>\n      <tr>\n        <td>Type IV<\/td>\n        <td>Urea-Melamine Blend<\/td>\n        <td>~3.7<\/td>\n        <td>Intermediate applications; specialty use<\/td>\n        <td>Specialty suppliers only<\/td>\n      <\/tr>\n      <tr>\n        <td>Type V<\/td>\n        <td>Acrylic (PMMA)<\/td>\n        <td>~3.0<\/td>\n        <td><strong>CFRP composites, radomes<\/strong>, sensitive structures; essential for composite-intensive aircraft<\/td>\n        <td>Available; higher cost<\/td>\n      <\/tr>\n    <\/tbody>\n  <\/table>\n<\/div>\n\n<p>For each type, MIL-P-85891A specifies minimum performance requirements including: particle size distribution (percentage passing and retained at each mesh screen), bulk density limits, moisture content (\u22641.0% for Type II), pH range (7.0\u20139.0 for Type II), free formaldehyde content (\u22640.1%), and hardness verification. Suppliers must provide a Certificate of Conformance (CoC) for each lot shipped, documenting lot-specific test results against each specification requirement.<\/p>\n\n<div class=\"pm-callout pm-callout-warn\">\n  <strong>Procurement note:<\/strong> MIL-P-85891A is a performance specification, not a source-qualification document. Any supplier can claim their product meets MIL-P-85891A, but the claim is only meaningful if backed by actual lot test data documented in a CoC. For defense contracts, the CoC must reference the specific lot number, test dates, and individual test results for each MIL-P-85891A parameter. A generic &#8220;meets MIL-P-85891A&#8221; statement without supporting test data does not constitute adequate documentation for DoD maintenance records. See: <a href=\"https:\/\/hlh-js.com\/resource\/blog\/mil-spec-plastic-media-what-mil-p-85891a-means-for-buyers\/\">MIL-P-85891A Explained for Buyers<\/a>.\n<\/div>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 4 \u2014 COATING SYSTEMS\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-coating-systems\">Aerospace Coating Systems Being Removed<\/h2>\n\n<p>Understanding what is being removed is essential to selecting correct blast parameters. Military and commercial aircraft carry multi-layer coating systems whose individual layers differ significantly in hardness, adhesion, and resistance to abrasive removal:<\/p>\n\n<div class=\"pm-coating-stack\">\n  <div class=\"pm-coating-layer\">\n    <div class=\"cl-num\" style=\"background:#475569\">5<\/div>\n    <div class=\"cl-name\">Topcoat (Exterior)<\/div>\n    <div class=\"cl-spec\">MIL-PRF-85285 polyurethane (military) or commercial equivalent. High-gloss or camouflage. UV-resistant. The outermost, most visible layer.<\/div>\n    <div class=\"cl-thick\">1.0\u20132.5 mil<\/div>\n  <\/div>\n  <div class=\"pm-coating-layer\">\n    <div class=\"cl-num\" style=\"background:#64748b\">4<\/div>\n    <div class=\"cl-name\">Intermediate Coat<\/div>\n    <div class=\"cl-spec\">MIL-PRF-85285 or MIL-DTL-53022 epoxy intermediate. Not always present; used on camouflage schemes and some commercial liveries for color blocking.<\/div>\n    <div class=\"cl-thick\">0.5\u20131.5 mil<\/div>\n  <\/div>\n  <div class=\"pm-coating-layer\">\n    <div class=\"cl-num\" style=\"background:#854d0e\">3<\/div>\n    <div class=\"cl-name\">Primer (Chromate)<\/div>\n    <div class=\"cl-spec\">MIL-PRF-23377 zinc chromate or barium chromate epoxy primer. Critical corrosion protection layer. Contains hexavalent chromium \u2014 regulated carcinogen requiring special handling when removed.<\/div>\n    <div class=\"cl-thick\">0.5\u20131.0 mil<\/div>\n  <\/div>\n  <div class=\"pm-coating-layer\">\n    <div class=\"cl-num\" style=\"background:#1e3a8a\">2<\/div>\n    <div class=\"cl-name\">Primer (Non-Chromate)<\/div>\n    <div class=\"cl-spec\">MIL-PRF-23377 non-chromate variants or MIL-PRF-85582 waterborne primer. Increasingly common as chromate replacements on newer aircraft and repaints.<\/div>\n    <div class=\"cl-thick\">0.5\u20131.0 mil<\/div>\n  <\/div>\n  <div class=\"pm-coating-layer\">\n    <div class=\"cl-num\" style=\"background:#15803d\">1<\/div>\n    <div class=\"cl-name\">Conversion Coating<\/div>\n    <div class=\"cl-spec\">Chromate conversion (Alodine\/Iridite) per MIL-DTL-81706 or anodize per MIL-A-8625. Chemically bonded to aluminum \u2014 not a free-standing film. Remains on substrate after depaint; protects bare metal between paint applications.<\/div>\n    <div class=\"cl-thick\">0.01\u20130.05 mil<\/div>\n  <\/div>\n  <div class=\"pm-coating-layer\">\n    <div class=\"cl-num\" style=\"background:#374151\">0<\/div>\n    <div class=\"cl-name\">Substrate<\/div>\n    <div class=\"cl-spec\">2024-T3 or 7075-T6 aluminum alloy (skin), Ti-6Al-4V titanium (fasteners, attachments), or CFRP composite (control surfaces, fairings). Must be unchanged by depaint process.<\/div>\n    <div class=\"cl-thick\">\u2014<\/div>\n  <\/div>\n<\/div>\n\n<p>The depaint objective is complete removal of layers 2\u20135 (all paint and primer layers) while leaving the conversion coating (layer 1) and substrate (layer 0) intact. This is the precise operational requirement that plastic media blasting is engineered to meet \u2014 and that chemical stripping, for all its drawbacks, achieves through a different mechanism (chemical dissolution rather than mechanical abrasion).<\/p>\n\n<div class=\"pm-callout pm-callout-warn\">\n  <strong>Chromate primer handling:<\/strong> When stripping aircraft that carry MIL-PRF-23377 chromate primers, all blast personnel must have hexavalent chromium exposure monitoring and medical surveillance per OSHA Standard 29 CFR 1910.1026. The blast media waste stream from chromate primer removal is a regulated hazardous waste (RCRA D007 \u2014 chromium). Waste characterization and disposal must be documented. This is not optional compliance \u2014 it is a condition of operation for any aerospace depaint facility.\n<\/div>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 5 \u2014 SUBSTRATES\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-substrates\">Aircraft Substrate Alloys &amp; Media Compatibility<\/h2>\n\n<p>Modern military and commercial aircraft use a range of structural materials, each with different hardness characteristics and blast media requirements:<\/p>\n\n<div class=\"pm-alloy-grid\">\n  <div class=\"pm-alloy-card\">\n    <div class=\"pm-alloy-head primary\">\u2705 2024-T3 Aluminum<\/div>\n    <div class=\"pm-alloy-body\">The most common aircraft skin alloy. Mohs ~2.8. Fully compatible with Type II urea Mesh 20\u201330 at 30\u201355 PSI. Primary target for most military depaint programs. Surface profile produced: 0.5\u20131.0 mil \u2014 within MIL-SPEC re-prime range.<\/div>\n  <\/div>\n  <div class=\"pm-alloy-card\">\n    <div class=\"pm-alloy-head primary\">\u2705 7075-T6 Aluminum<\/div>\n    <div class=\"pm-alloy-body\">High-strength wing spar caps, heavily loaded structure. Slightly harder than 2024-T3. Same media and parameters as 2024-T3 at standard aerospace depaint conditions. Fatigue-sensitive; process qualification essential.<\/div>\n  <\/div>\n  <div class=\"pm-alloy-card\">\n    <div class=\"pm-alloy-head primary\">\u2705 6061-T6 Aluminum<\/div>\n    <div class=\"pm-alloy-body\">Secondary structures, fittings, fairings. Similar hardness to 2024-T3. Compatible with standard Type II urea parameters. Less fatigue-critical than primary structure; somewhat more forgiving process window.<\/div>\n  <\/div>\n  <div class=\"pm-alloy-card\">\n    <div class=\"pm-alloy-head secondary\">\ud83d\udd35 7050-T7451 \/ 7475-T7351<\/div>\n    <div class=\"pm-alloy-body\">High-toughness variants used in modern aircraft structures. Slightly higher fatigue life than 7075-T6. Same media specification; qualification testing particularly important as these alloys are used in fracture-critical applications.<\/div>\n  <\/div>\n  <div class=\"pm-alloy-card\">\n    <div class=\"pm-alloy-head secondary\">\ud83d\udd35 Ti-6Al-4V Titanium<\/div>\n    <div class=\"pm-alloy-body\">Engine nacelles, hot section firewalls, high-strength fittings. Mohs ~6 \u2014 much harder than plastic media. Fully compatible with any plastic blast type at any practical pressure. Type II or III appropriate. No substrate damage risk.<\/div>\n  <\/div>\n  <div class=\"pm-alloy-card\">\n    <div class=\"pm-alloy-head secondary\">\ud83d\udd35 Stainless Steel (300-series)<\/div>\n    <div class=\"pm-alloy-body\">Control cables, fasteners, some firewall panels. Fully compatible with plastic blast. No iron contamination risk (important for stainless). Type II urea at standard parameters appropriate.<\/div>\n  <\/div>\n  <div class=\"pm-alloy-card\">\n    <div class=\"pm-alloy-head caution\">\u26a0\ufe0f CFRP Composites<\/div>\n    <div class=\"pm-alloy-body\">Control surfaces, fairings, modern fuselage sections (787, A350). Requires Type V Acrylic only. No Type II or III without explicit engineering approval and narrow-window process qualification. See composite section below.<\/div>\n  <\/div>\n  <div class=\"pm-alloy-card\">\n    <div class=\"pm-alloy-head caution\">\u26a0\ufe0f Fiberglass \/ GFRP<\/div>\n    <div class=\"pm-alloy-body\">Radomes, fairings, secondary panels. Type V Acrylic preferred; Type II at very low pressure (20\u201330 PSI) with fine mesh may be acceptable per specific process approval. Always verify against applicable maintenance manual.<\/div>\n  <\/div>\n  <div class=\"pm-alloy-card\">\n    <div class=\"pm-alloy-head special\">\ud83d\udfe3 Honeycomb Sandwich Panels<\/div>\n    <div class=\"pm-alloy-body\">Composite or aluminum face skins over Nomex or aluminum honeycomb core. Face skins are thin (1\u20133 plies). Process parameters must be qualified for the specific panel construction \u2014 thin face skins have very narrow damage-free blast windows. Type V acrylic on composite faces; Type II at minimum parameters on thin aluminum faces.<\/div>\n  <\/div>\n<\/div>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 6 \u2014 ZONE BY ZONE\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-zones\">Zone-by-Zone: Different Areas, Different Requirements<\/h2>\n\n<p>An aircraft is not a uniform structure. Different zones have different substrate materials, coating systems, access constraints, and structural criticality \u2014 each of which affects the appropriate blast media and process parameters. Here is how a typical military aircraft breaks down by depaint zone:<\/p>\n\n<div class=\"pm-aircraft-zones\">\n  <div class=\"pm-zone-row\">\n    <div class=\"pm-zone-label\"><span class=\"zone-icon\">\ud83d\udeeb<\/span>Fuselage Skin (Aluminum)<\/div>\n    <div class=\"pm-zone-detail\">\n      <span class=\"zd-media\">Type II Urea \u00b7 Mesh 20\u201330 \u00b7 35\u201355 PSI<\/span>\n      <span class=\"zd-note\">Primary depaint area. Largest surface area. Standard parameters for 2024-T3 and 7075-T6. Work top-to-bottom in sections; maintain consistent nozzle speed to prevent streaking.<\/span>\n    <\/div>\n  <\/div>\n  <div class=\"pm-zone-row\">\n    <div class=\"pm-zone-label\"><span class=\"zone-icon\">\u2708\ufe0f<\/span>Wing Upper\/Lower Surfaces<\/div>\n    <div class=\"pm-zone-detail\">\n      <span class=\"zd-media\">Type II Urea \u00b7 Mesh 20\u201330 \u00b7 30\u201350 PSI<\/span>\n      <span class=\"zd-note\">Fatigue-critical primary structure. Process qualification documentation required. Maintain consistent standoff; avoid dwell. Post-blast fatigue assessment may be required per aircraft maintenance manual.<\/span>\n    <\/div>\n  <\/div>\n  <div class=\"pm-zone-row\">\n    <div class=\"pm-zone-label\"><span class=\"zone-icon\">\ud83d\udd37<\/span>Control Surfaces (Metal)<\/div>\n    <div class=\"pm-zone-detail\">\n      <span class=\"zd-media\">Type II Urea \u00b7 Mesh 30 \u00b7 25\u201340 PSI<\/span>\n      <span class=\"zd-note\">Often thinner gauge than fuselage skin. Reduce pressure 10\u201315 PSI from fuselage parameters. Remove balance weights before blasting \u2014 protect bearing surfaces with masking.<\/span>\n    <\/div>\n  <\/div>\n  <div class=\"pm-zone-row\">\n    <div class=\"pm-zone-label\"><span class=\"zone-icon\">\ud83d\udd36<\/span>Control Surfaces (CFRP)<\/div>\n    <div class=\"pm-zone-detail\">\n      <span class=\"zd-media\">Type V Acrylic \u00b7 Mesh 30\u201350 \u00b7 20\u201335 PSI<\/span>\n      <span class=\"zd-note\">Common on tactical aircraft elevators, rudders, ailerons. Requires Type V acrylic and separate process qualification from metal zones. Monitor for fiber whitening every pass.<\/span>\n    <\/div>\n  <\/div>\n  <div class=\"pm-zone-row\">\n    <div class=\"pm-zone-label\"><span class=\"zone-icon\">\ud83d\udce1<\/span>Radome<\/div>\n    <div class=\"pm-zone-detail\">\n      <span class=\"zd-media\">Type V Acrylic \u00b7 Mesh 40\u201360 \u00b7 15\u201330 PSI<\/span>\n      <span class=\"zd-note\">Fiberglass or CFRP-sandwich construction. Mandatory electrical transmission test after depaint per radome maintenance manual. Do not blast within defined exclusion zones around antenna feed.<\/span>\n    <\/div>\n  <\/div>\n  <div class=\"pm-zone-row\">\n    <div class=\"pm-zone-label\"><span class=\"zone-icon\">\ud83d\udd25<\/span>Engine Nacelle (Titanium)<\/div>\n    <div class=\"pm-zone-detail\">\n      <span class=\"zd-media\">Type II or III \u00b7 Mesh 16\u201330 \u00b7 40\u201360 PSI<\/span>\n      <span class=\"zd-note\">Titanium substrate tolerates more aggressive media and pressure. Higher strip rate justifiable. Cap and mask all engine interface flanges, sensor ports, and bleed air fittings before blasting.<\/span>\n    <\/div>\n  <\/div>\n  <div class=\"pm-zone-row\">\n    <div class=\"pm-zone-label\"><span class=\"zone-icon\">\ud83d\udd29<\/span>Vertical\/Horizontal Stabilizer<\/div>\n    <div class=\"pm-zone-detail\">\n      <span class=\"zd-media\">Type II Urea \u00b7 Mesh 20\u201330 \u00b7 30\u201350 PSI<\/span>\n      <span class=\"zd-note\">Mixed construction common (aluminum ribs and spars, possibly CFRP skins on modern aircraft). Verify skin material before blasting. Use composite parameters if any CFRP skin is present.<\/span>\n    <\/div>\n  <\/div>\n  <div class=\"pm-zone-row\">\n    <div class=\"pm-zone-label\"><span class=\"zone-icon\">\ud83d\udeaa<\/span>Access Doors &amp; Panels<\/div>\n    <div class=\"pm-zone-detail\">\n      <span class=\"zd-media\">Type II Urea \u00b7 Mesh 30 \u00b7 25\u201340 PSI<\/span>\n      <span class=\"zd-note\">Often thin-gauge aluminum or CFRP. Remove from aircraft before blasting where possible; if blasted in-situ, protect surrounding structure with rigid masking. Verify hinge and latch hardware removal or masking.<\/span>\n    <\/div>\n  <\/div>\n  <div class=\"pm-zone-row\">\n    <div class=\"pm-zone-label\"><span class=\"zone-icon\">\ud83d\udeec<\/span>Landing Gear Bay<\/div>\n    <div class=\"pm-zone-detail\">\n      <span class=\"zd-media\">Type II Urea \u00b7 Mesh 20 \u00b7 40\u201355 PSI<\/span>\n      <span class=\"zd-note\">Complex geometry with structural members, hydraulic lines, wiring runs. All hydraulics and electrical must be protected or removed. Post-blast inspection for media retention in crevices is critical \u2014 trapped media causes corrosion under paint.<\/span>\n    <\/div>\n  <\/div>\n<\/div>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 7 \u2014 MILITARY\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-military\">Military Aircraft Depainting<\/h2>\n\n<div class=\"pm-sector-grid\">\n  <div class=\"pm-sector-card\">\n    <div class=\"pm-sector-head mil\">\n      \u2708\ufe0f Military Depaint Program\n      <div class=\"sh-sub\">DoD Depot &amp; Field-Level Maintenance<\/div>\n    <\/div>\n    <div class=\"pm-sector-body\">\n      <ul>\n        <li><strong>Primary driver:<\/strong> Corrosion control and inspection access \u2014 stripping exposes all substrate surfaces for Non-Destructive Inspection (NDI)<\/li>\n        <li><strong>Depaint interval:<\/strong> 2\u20135 years depending on platform, operational environment, and inspection requirements<\/li>\n        <li><strong>Governing documents:<\/strong> Aircraft-specific Technical Orders (TO), weapon system maintenance manuals, depot process specifications<\/li>\n        <li><strong>Media specification:<\/strong> MIL-P-85891A mandatory; Certificate of Conformance required per lot<\/li>\n        <li><strong>Process control:<\/strong> Written process specification required; operator qualification and recurring training<\/li>\n        <li><strong>Chromate management:<\/strong> Full OSHA and EPA compliance required; medical surveillance for operators<\/li>\n        <li><strong>Post-strip inspection:<\/strong> NDI (eddy current, penetrant, ultrasonic) before repaint; fatigue life assessment for primary structure<\/li>\n        <li><strong>Examples:<\/strong> F-16, F\/A-18, C-130, B-52, CH-47, UH-60, P-8<\/li>\n      <\/ul>\n    <\/div>\n  <\/div>\n  <div class=\"pm-sector-card\">\n    <div class=\"pm-sector-head civil\">\n      \ud83d\udee9 Commercial Airline MRO\n      <div class=\"sh-sub\">Heavy Maintenance Visits (D-Check)<\/div>\n    <\/div>\n    <div class=\"pm-sector-body\">\n      <ul>\n        <li><strong>Primary driver:<\/strong> Livery repaint and corrosion inspection \u2014 airlines repaint on rebranding, lease return, and heavy maintenance cycles<\/li>\n        <li><strong>Depaint interval:<\/strong> 5\u20138 years, typically aligned with D-check (heavy maintenance visit)<\/li>\n        <li><strong>Governing documents:<\/strong> Aircraft Maintenance Manual (AMM), OEM service bulletins, EASA\/FAA-approved maintenance procedures<\/li>\n        <li><strong>Media specification:<\/strong> MIL-P-85891A or OEM-specified equivalent; airlines and MRO facilities specify in their Process Specifications (PS)<\/li>\n        <li><strong>Process control:<\/strong> Part 145 repair station requirements; approved data required for any process affecting airworthiness<\/li>\n        <li><strong>Composites:<\/strong> B787 (extensive CFRP fuselage), A350 require Type V acrylic for composite zones \u2014 growing requirement as composite-intensive aircraft age<\/li>\n        <li><strong>Examples:<\/strong> B737, B757, B767, B787, A320, A330, A350, A380<\/li>\n      <\/ul>\n    <\/div>\n  <\/div>\n<\/div>\n\n<p>The military and commercial sectors share the same underlying plastic media technology but differ significantly in their regulatory frameworks, documentation requirements, and technical authority structures. Military depaint processes are controlled through Technical Orders (TOs) approved by the respective service&#8217;s engineering authority. Commercial processes are controlled through OEM-approved Aircraft Maintenance Manual procedures and Part 145 repair station process specifications, with FAA or EASA oversight.<\/p>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 8 \u2014 COMMERCIAL\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-commercial\">Commercial Airline Heavy Maintenance<\/h2>\n\n<p>For commercial airlines, the full-aircraft depaint and repaint cycle is typically integrated into the D-check (also called 12-year check or heavy maintenance visit depending on operator and OEM terminology), which is the most comprehensive scheduled maintenance event in an aircraft&#8217;s life cycle. The aircraft is completely stripped of all interior components, systems are opened for inspection, and the exterior is fully deprimed and repainted.<\/p>\n\n<p>The commercial depaint context differs from military in several important ways that affect how plastic media blasting is applied:<\/p>\n\n<h3>Livery Economics<\/h3>\n<p>For commercial operators, depaint and repaint is not just a maintenance event \u2014 it is a significant brand and appearance investment. Airlines typically spend $150,000\u2013$400,000 per aircraft on a full repaint, depending on aircraft size and livery complexity. This investment creates a strong incentive to deliver bare metal surfaces that are uniformly clean, dimensionally unchanged, and immediately ready for primer application \u2014 which is precisely what a well-controlled plastic media blast process provides. Any depaint method that introduces new defects (warped panels, thinned areas, residual contamination) adds body work and repair costs that erode the economics of the repaint investment.<\/p>\n\n<h3>OEM Involvement<\/h3>\n<p>Major commercial aircraft OEMs \u2014 Boeing, Airbus, Embraer, Bombardier \u2014 have each issued maintenance documentation covering plastic media blasting parameters for their specific aircraft. These documents are incorporated into the Aircraft Maintenance Manual (AMM) and constitute the approved technical basis for depaint operations at Part 145 repair stations. Any deviation from AMM-specified parameters requires an Engineering Order (EO) or equivalent approved-data document. MRO facilities performing commercial depaint work must hold appropriate approvals and operate within AMM parameters \u2014 using a process that has not been validated against the specific aircraft type is not acceptable under Part 145 repair station quality systems.<\/p>\n\n<h3>Composite-Intensive Modern Aircraft<\/h3>\n<p>The Boeing 787 and Airbus A350 represent a step change in commercial aircraft construction \u2014 both use CFRP for approximately 50% of their primary structure by weight, including large sections of the fuselage barrel. These aircraft require fundamentally different depaint strategies from aluminum-dominated legacy types, with Type V acrylic media used across all composite zones and carefully managed transition protocols at the interfaces between composite fuselage sections and aluminum structural elements. As these aircraft age into their first D-check cycles (2025 onward for the earliest 787s), the commercial MRO industry is building the process experience and facility infrastructure to handle composite-intensive aircraft at scale.<\/p>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 9 \u2014 COMPOSITE\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-composite\">Composite Structure Depainting<\/h2>\n\n<p>The depainting of composite aircraft structures \u2014 CFRP panels, fiberglass fairings, Nomex-core sandwich structures \u2014 represents the most technically demanding application of plastic blast media in aerospace maintenance, and the one where process qualification rigor matters most. The substrate damage mechanisms, qualification requirements, and post-blast inspection methods for composite depainting are distinct from those for metallic structures.<\/p>\n\n<p>The two primary damage modes for CFRP under blast operations are fiber severance (individual carbon fibers cut by abrasive particle impact) and interlaminar delamination (separation of plies driven by blast shockwave energy). Both forms of damage reduce structural performance in ways that cannot be detected by visual inspection \u2014 a CFRP panel can appear undamaged externally while carrying significant internal delamination. This is why composite depaint process qualification requires ultrasonic C-scan inspection before and after the qualification blast sequence, not just visual inspection.<\/p>\n\n<p>Type V acrylic media is required for all bare CFRP depaint operations. The combination of PMMA&#8217;s thermoplastic deformation behavior and lower particle density reduces peak substrate stress to the level where coating removal can be achieved without initiating fiber or matrix damage within the qualified process window. Type II urea can be used on CFRP at very low pressures (15\u201325 PSI) per some process approvals, but the process window is significantly narrower and the risk of operator variation-induced damage is substantially higher.<\/p>\n\n<p>For composite depainting process qualification, the minimum accepted test sequence typically includes:<\/p>\n<ul>\n  <li>Baseline C-scan and visual inspection of representative composite coupons<\/li>\n  <li>Blast sequence at proposed parameters (typically 3\u20135 full coating removal passes)<\/li>\n  <li>Post-blast C-scan comparison to detect any delamination not present in baseline<\/li>\n  <li>Microscopic cross-section examination of blasted surface at 40\u2013100\u00d7 to check fiber condition<\/li>\n  <li>Mechanical testing (if structurally critical application): open-hole tension or compression after blast vs. unblasted baseline<\/li>\n  <li>Environmental testing: temperature cycling and humidity soak of blasted coupons to detect latent delamination propagation in service conditions<\/li>\n<\/ul>\n\n<p>Full guidance: <a href=\"https:\/\/hlh-js.com\/resource\/blog\/acrylic-type-v-plastic-media-for-sensitive-surfaces\/\">Acrylic (Type V) Plastic Media for Sensitive Surfaces<\/a>.<\/p>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 10 \u2014 PARAMETERS\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-parameters\">Qualified Blast Parameters<\/h2>\n\n<p>These parameter ranges represent the consensus of established aerospace depaint process specifications for the most common aircraft structural materials. They are starting points for process qualification, not substitutes for aircraft-specific maintenance manual requirements:<\/p>\n\n<div class=\"pm-param-grid\">\n  <div class=\"pm-param-card\">\n    <div class=\"pm-param-value\">30\u201355<\/div>\n    <div class=\"pm-param-unit\">PSI<\/div>\n    <div class=\"pm-param-label\">2024-T3 \/ 7075-T6 aluminum skin (Type II Urea, Mesh 20\u201330)<\/div>\n  <\/div>\n  <div class=\"pm-param-card\">\n    <div class=\"pm-param-value\">20\u201335<\/div>\n    <div class=\"pm-param-unit\">PSI<\/div>\n    <div class=\"pm-param-label\">CFRP composites (Type V Acrylic, Mesh 30\u201350)<\/div>\n  <\/div>\n  <div class=\"pm-param-card\">\n    <div class=\"pm-param-value\">40\u201365<\/div>\n    <div class=\"pm-param-unit\">PSI<\/div>\n    <div class=\"pm-param-label\">Titanium alloy (Type II or III, Mesh 20\u201330)<\/div>\n  <\/div>\n  <div class=\"pm-param-card\">\n    <div class=\"pm-param-value\">6\u201310<\/div>\n    <div class=\"pm-param-unit\">inches<\/div>\n    <div class=\"pm-param-label\">Standoff distance, all metallic substrates<\/div>\n  <\/div>\n  <div class=\"pm-param-card\">\n    <div class=\"pm-param-value\">8\u201312<\/div>\n    <div class=\"pm-param-unit\">inches<\/div>\n    <div class=\"pm-param-label\">Standoff distance, composite substrates<\/div>\n  <\/div>\n  <div class=\"pm-param-card\">\n    <div class=\"pm-param-value\">75\u201390<\/div>\n    <div class=\"pm-param-unit\">degrees<\/div>\n    <div class=\"pm-param-label\">Impingement angle, metallic substrates<\/div>\n  <\/div>\n  <div class=\"pm-param-card\">\n    <div class=\"pm-param-value\">60\u201380<\/div>\n    <div class=\"pm-param-unit\">degrees<\/div>\n    <div class=\"pm-param-label\">Impingement angle, composite substrates (never 90\u00b0)<\/div>\n  <\/div>\n  <div class=\"pm-param-card\">\n    <div class=\"pm-param-value\">&lt;1.0<\/div>\n    <div class=\"pm-param-unit\">mil (25 \u00b5m)<\/div>\n    <div class=\"pm-param-label\">Maximum surface profile on aluminum skin (per most MIL-SPEC re-prime specifications)<\/div>\n  <\/div>\n<\/div>\n\n<div class=\"pm-callout pm-callout-danger\">\n  <strong>Critical compliance note:<\/strong> These parameter ranges are general guidance. The authoritative parameters for any specific aircraft type are found in that aircraft&#8217;s Technical Order (military) or Aircraft Maintenance Manual (commercial). In all cases where the aircraft maintenance documentation specifies parameters that differ from general guidance, the aircraft documentation governs. Do not extrapolate parameters from one aircraft type to another without engineering authority approval.\n<\/div>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 11 \u2014 PROCESS STEP BY STEP\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-process\">The Qualified Depaint Process: Step by Step<\/h2>\n\n<div class=\"pm-compliance-flow\">\n\n  <div class=\"pm-cf-step\">\n    <div class=\"pm-cf-left\">\n      <div class=\"pm-cf-dot\">1<\/div>\n      <div class=\"pm-cf-line\"><\/div>\n    <\/div>\n    <div class=\"pm-cf-body\">\n      <h4>Work Order and Documentation Setup<\/h4>\n      <p>Before any blast work begins, establish the formal work order referencing the applicable Technical Order (military) or AMM procedure number (commercial). Verify that the operator performing the work is qualified per the applicable process specification \u2014 aerospace depaint operators typically require documented initial training and recurring annual qualification on the specific process and aircraft type. Record media lot number and Certificate of Conformance data in the work order.<\/p>\n      <div class=\"cf-doc\">\ud83d\udccb Required Doc: Work Order \u00b7 CoC \u00b7 Operator Qualification Record<\/div>\n    <\/div>\n  <\/div>\n\n  <div class=\"pm-cf-step\">\n    <div class=\"pm-cf-left\">\n      <div class=\"pm-cf-dot\">2<\/div>\n      <div class=\"pm-cf-line\"><\/div>\n    <\/div>\n    <div class=\"pm-cf-body\">\n      <h4>Aircraft Preparation and Protection<\/h4>\n      <p>Position aircraft in the blast hangar on approved jacks or ground support. Close all fuel and oil filler caps. Install blanking plates on all engine inlets, exhaust nozzles, environmental control system ports, and pitot-static system probes. Mask all windows (cockpit and cabin) with rigid backing panels \u2014 never rely on masking tape and paper alone for glass protection. Remove or mask all rubber seals, antenna waveguides, and composite components that require different media parameters than the main fuselage skin. Remove landing gear, flight control hinges, and other movable components that would shadow blast zones or trap media.<\/p>\n      <div class=\"cf-doc\">\ud83d\udccb Required Doc: Masking\/Protection Checklist<\/div>\n      <p class=\"cf-tip\">Most aircraft maintenance manuals include a specific masking diagram as an approved data reference \u2014 use it, do not improvise.<\/p>\n    <\/div>\n  <\/div>\n\n  <div class=\"pm-cf-step\">\n    <div class=\"pm-cf-left\">\n      <div class=\"pm-cf-dot\">3<\/div>\n      <div class=\"pm-cf-line\"><\/div>\n    <\/div>\n    <div class=\"pm-cf-body\">\n      <h4>Equipment Calibration and Media Verification<\/h4>\n      <p>Verify nozzle pressure at the nozzle inlet with an inline gauge \u2014 not at the compressor regulator. Set pressure to the lower end of the applicable range for the zone being worked. Inspect nozzle for wear; replace if bore is more than 1\/16-inch oversize. Verify media type and mesh size match the zone specification. Check media moisture by observing flow \u2014 clumping or erratic nozzle output indicates moisture contamination requiring media replacement. Run the reclaim system through one dry cycle to verify air wash separator and screen deck are functioning correctly before loading production parts.<\/p>\n      <div class=\"cf-doc\">\ud83d\udccb Required Doc: Equipment Calibration Record \u00b7 Nozzle Wear Log<\/div>\n    <\/div>\n  <\/div>\n\n  <div class=\"pm-cf-step\">\n    <div class=\"pm-cf-left\">\n      <div class=\"pm-cf-dot\">4<\/div>\n      <div class=\"pm-cf-line\"><\/div>\n    <\/div>\n    <div class=\"pm-cf-body\">\n      <h4>Trial Blast on Qualification Area<\/h4>\n      <p>Before proceeding to flight-critical structure, perform a trial blast on a non-critical area of the same substrate material (inner fuselage skin panel in a wheel well, for example) at the target parameters. Inspect the trial area for complete coating removal and measure surface profile with Testex Press-O-Film replica tape. If profile exceeds the maximum specified in the maintenance manual (typically 0.5\u20131.0 mil for aluminum), reduce pressure or increase mesh fineness before proceeding to primary structure. Document trial area location and measurements in the work order.<\/p>\n      <div class=\"cf-doc\">\ud83d\udccb Required Doc: Trial Blast Record \u00b7 Surface Profile Measurement<\/div>\n    <\/div>\n  <\/div>\n\n  <div class=\"pm-cf-step\">\n    <div class=\"pm-cf-left\">\n      <div class=\"pm-cf-dot\">5<\/div>\n      <div class=\"pm-cf-line\"><\/div>\n    <\/div>\n    <div class=\"pm-cf-body\">\n      <h4>Systematic Blast Sequence<\/h4>\n      <p>Work the aircraft in defined zones \u2014 typically starting at the fuselage nose and working aft, then upper wing surfaces, lower wing, vertical and horizontal stabilizers, and finally nacelles and pylons. Within each zone, blast in overlapping passes with consistent nozzle travel speed. Transition to composite-specific parameters (Type V Acrylic, lower pressure) when moving from metallic to composite zones \u2014 never use metallic parameters on composite surfaces. Document zone completion as each area is cleared.<\/p>\n      <p>At rivet lines, lap joints, and skin doublers, pay particular attention to complete coating removal in the recessed areas at joint edges. These are common locations where primer residue remains after the main skin is stripped, creating adhesion discontinuities in the subsequent repaint.<\/p>\n      <div class=\"cf-doc\">\ud83d\udccb Required Doc: Zone Completion Checklist<\/div>\n    <\/div>\n  <\/div>\n\n  <div class=\"pm-cf-step\">\n    <div class=\"pm-cf-left\">\n      <div class=\"pm-cf-dot\">6<\/div>\n      <div class=\"pm-cf-line\"><\/div>\n    <\/div>\n    <div class=\"pm-cf-body\">\n      <h4>Post-Blast Inspection<\/h4>\n      <p>After blasting is complete, blow off all media dust with clean dry compressed air using a fan nozzle to avoid concentrated pressure on bare skin. Perform a complete visual inspection of the bare substrate under adequate lighting (minimum 50 foot-candles at the inspection surface). Use UV light to detect any residual fluorescent primer (if the aircraft was painted with a fluorescent-penetrant-compatible primer). Inspect all fastener holes for media entrapment. Inspect the conversion coating condition \u2014 chromate conversion coating should appear as a uniform golden-tan color; local discoloration may indicate areas that received insufficient blast energy or areas where the conversion coat was disturbed.<\/p>\n      <div class=\"cf-doc\">\ud83d\udccb Required Doc: Visual Inspection Record \u00b7 UV Inspection Record<\/div>\n      <p class=\"cf-tip\">On high-cycle aircraft, the post-blast inspection window is also when Non-Destructive Inspection (eddy current, fluorescent penetrant, ultrasonic) of fatigue-critical structure is performed before re-prime \u2014 coordinate NDI scheduling before stripping so NDI personnel can access the bare structure immediately after blast.<\/p>\n    <\/div>\n  <\/div>\n\n  <div class=\"pm-cf-step\">\n    <div class=\"pm-cf-left\">\n      <div class=\"pm-cf-dot\">7<\/div>\n      <div class=\"pm-cf-line\"><\/div>\n    <\/div>\n    <div class=\"pm-cf-body\">\n      <h4>Surface Treatment and Prime Window Management<\/h4>\n      <p>Bare aluminum begins oxidizing immediately after blasting. The maximum allowable time between bare metal exposure and primer application is specified in the applicable maintenance document \u2014 commonly 4 hours in controlled hangar conditions (below 75\u00b0F \/ 24\u00b0C and below 60% RH), and as short as 2 hours in humid or warm conditions. Apply corrosion-inhibiting compound (CIC) or touch-up conversion coating to any areas where the original chromate conversion coating has been disturbed. Apply primer (typically MIL-PRF-23377 chromate or approved non-chromate equivalent) within the specified window. Document primer lot number and application time in the work order.<\/p>\n      <div class=\"cf-doc\">\ud83d\udccb Required Doc: Primer Application Record \u00b7 Environmental Conditions Log (temp\/humidity at time of application)<\/div>\n    <\/div>\n  <\/div>\n\n<\/div>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 12 \u2014 VS CHEMICAL\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-vs-chemical\">Plastic Media vs Chemical Stripping: Full Comparison<\/h2>\n\n<div class=\"pm-chem-compare\">\n  <div class=\"pm-chem-col\">\n    <div class=\"pm-chem-head plastic\">\u2705 Plastic Media Blasting<\/div>\n    <div class=\"pm-chem-body\">\n      <ul>\n        <li><strong>Environmental:<\/strong> No liquid chemical waste stream; dry process. Solid waste (media + paint) is manageable under solid waste regulations (unless chromate-contaminated)<\/li>\n        <li><strong>Operator safety:<\/strong> Physical blast hazard (PPE required) but no chemical exposure from the stripping agent itself; primary chemical hazard is from stripped coating residue<\/li>\n        <li><strong>Strip time:<\/strong> 4\u201312 hours for a typical fighter aircraft; 12\u201324 hours for a large transport<\/li>\n        <li><strong>Surface profile:<\/strong> Controlled 0.5\u20131.0 mil profile produced \u2014 ready for primer without additional surface conditioning<\/li>\n        <li><strong>Substrate effect:<\/strong> No metal removal; no hydrogen embrittlement risk; no seam penetration<\/li>\n        <li><strong>Composite compatibility:<\/strong> Excellent (Type V Acrylic); only practical dry stripping method for CFRP<\/li>\n        <li><strong>Cost per aircraft:<\/strong> Generally lower than chemical, especially when waste disposal costs are included<\/li>\n        <li><strong>\u041e\u0433\u0440\u0430\u043d\u0438\u0447\u0435\u043d\u0438\u044f:<\/strong> Cannot reach inside sealed structure; line-of-sight only; requires blast hangar infrastructure<\/li>\n      <\/ul>\n    <\/div>\n  <\/div>\n  <div class=\"pm-chem-col\">\n    <div class=\"pm-chem-head chemical\">\u26a0\ufe0f Chemical Stripping<\/div>\n    <div class=\"pm-chem-body\">\n      <ul>\n        <li><strong>Environmental:<\/strong> Large volume liquid hazardous waste; complex wastewater treatment required; methylene chloride (MCL) restricted by EPA Significant New Use Rule<\/li>\n        <li><strong>Operator safety:<\/strong> Skin, eye, and respiratory exposure risk to caustic strippers and dissolved chromate primer; full chemical PPE required throughout process<\/li>\n        <li><strong>Strip time:<\/strong> 8\u201348 hours depending on dwell time requirements; significant process variability<\/li>\n        <li><strong>Surface profile:<\/strong> Chemical dissolution leaves near-zero profile; conversion coat may be attacked; requires phosphoric acid etch or re-conversion before prime in many processes<\/li>\n        <li><strong>Substrate effect:<\/strong> Risk of hydrogen embrittlement on high-strength aluminum from acidic strippers; seam penetration may damage seam sealant and spot weld adhesive<\/li>\n        <li><strong>Composite compatibility:<\/strong> Chemical strippers attack CFRP resin systems; generally incompatible with CFRP composites<\/li>\n        <li><strong>Cost per aircraft:<\/strong> High chemical and waste disposal costs; falling out of use for economic and regulatory reasons<\/li>\n        <li><strong>\u041f\u0440\u0435\u0438\u043c\u0443\u0449\u0435\u0441\u0442\u0432\u0430:<\/strong> Reaches inside sealed cavities; can remove coatings in areas inaccessible to blast nozzle<\/li>\n      <\/ul>\n    <\/div>\n  <\/div>\n<\/div>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 13 \u2014 FATIGUE LIFE\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-fatigue\">Fatigue Life Considerations<\/h2>\n\n<p>The relationship between plastic media blasting and aircraft structural fatigue life is one of the most extensively studied technical questions in the history of this process, and the answer is nuanced enough to deserve a dedicated section.<\/p>\n\n<h3>The Research Baseline<\/h3>\n<p>Multiple studies conducted by the U.S. Air Force, the National Aeronautics and Space Administration, and independent research institutions in the 1980s and 1990s examined the effect of plastic media blasting on the fatigue life of aluminum alloy specimens representative of aircraft primary structure. The consistent finding was that <strong>plastic media blasting at parameters within the MIL-P-85891A-compliant process window does not produce a statistically significant reduction in fatigue life<\/strong> compared to pre-blast baseline specimens. Some studies found a slight fatigue life improvement, attributed to beneficial compressive residual stress introduced by the blast peening effect at the surface.<\/p>\n\n<h3>The Critical Caveat: Process Window Exceedance<\/h3>\n<p>The research finding above is bounded by the condition &#8220;within the qualified process window.&#8221; Blasting that exceeds the qualified parameter envelope \u2014 specifically, pressure above the specified maximum, mesh coarser than specified, or standoff closer than the minimum \u2014 can produce tensile residual stress at the surface rather than compressive, which does reduce fatigue life. The mechanism is straightforward: at excessive blast energy, the plastic deformation of the surface layer puts it in tension relative to the substrate below, creating a condition analogous to a tensile pre-load on the fatigue crack initiation region.<\/p>\n\n<p>This is why process control in aerospace depaint is not a bureaucratic preference \u2014 it is a structural engineering requirement. The parameters specified in the Technical Order or AMM are not conservative guidelines with room for operator judgment. They are the boundary conditions within which the structural safety of the aircraft is preserved. Nozzle pressure above the specified maximum, even for a brief period, puts the aircraft&#8217;s structural safety guarantee at risk in a way that cannot subsequently be detected by inspection.<\/p>\n\n<h3>Practical Implications<\/h3>\n<p>For organizations performing aerospace depaint operations, the fatigue life consideration drives three specific practices:<\/p>\n<ul>\n  <li><strong>Inline nozzle pressure gauging:<\/strong> Pressure must be measured at the nozzle, not inferred from the compressor setting. Hose pressure drop is real and variable; assuming nozzle pressure equals compressor pressure is an engineering error.<\/li>\n  <li><strong>Nozzle wear monitoring:<\/strong> Nozzle bore growth increases flow at a given compressor pressure, which raises nozzle velocity and effective blast energy. A worn nozzle operating at the &#8220;correct&#8221; compressor setting may be producing above-limit blast energy at the part surface.<\/li>\n  <li><strong>Documentation:<\/strong> Every blast operation on primary structure should be documented with actual measured nozzle pressure, media type and lot, mesh size, and zone worked. This documentation becomes part of the aircraft&#8217;s maintenance history and the structural engineering traceability record.<\/li>\n<\/ul>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 14 \u2014 DOCUMENTATION\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-docs\">Documentation &amp; Traceability Requirements<\/h2>\n\n<p>Aerospace depaint operations generate a documentation burden that is significantly higher than automotive or industrial blast work. This is not administrative overhead \u2014 it is the engineering traceability system that allows the aircraft&#8217;s maintenance history to be reconstructed and verified at any point in its service life.<\/p>\n\n<div class=\"pm-doc-grid\">\n  <div class=\"pm-doc-card\">\n    <div class=\"dc-icon\">\ud83d\udcc4<\/div>\n    <h4>Media Certificate of Conformance<\/h4>\n    <p>Lot-specific CoC documenting test results against every MIL-P-85891A parameter. Must reference media type, mesh size, lot number, manufacturer, and test dates. Retained in depot quality records for the life of the aircraft program.<\/p>\n  <\/div>\n  <div class=\"pm-doc-card\">\n    <div class=\"dc-icon\">\ud83e\udeaa<\/div>\n    <h4>Operator Qualification Record<\/h4>\n    <p>Documentation that the blast operator is trained and currently qualified per the applicable process specification. Typically requires initial training, supervised practice on qualification coupons, and annual recertification. Must be traceable to the specific aircraft maintenance record.<\/p>\n  <\/div>\n  <div class=\"pm-doc-card\">\n    <div class=\"dc-icon\">\ud83d\udccf<\/div>\n    <h4>Equipment Calibration Records<\/h4>\n    <p>Calibration status of pressure gauges (inline nozzle gauges must be calibrated on a defined interval \u2014 typically annually). Nozzle wear measurements recorded at defined intervals. Air wash separator calibration records. Dust collector performance records.<\/p>\n  <\/div>\n  <div class=\"pm-doc-card\">\n    <div class=\"dc-icon\">\ud83d\udd0d<\/div>\n    <h4>Trial Blast Records<\/h4>\n    <p>Documentation of trial blast location, parameters used, surface profile measurement result, and inspector signature. Required before beginning work on flight-critical structure on each aircraft. Cannot be carried over from a previous aircraft even of the same type.<\/p>\n  <\/div>\n  <div class=\"pm-doc-card\">\n    <div class=\"dc-icon\">\u2705<\/div>\n    <h4>Zone Completion Checklist<\/h4>\n    <p>Sequential sign-off of each blast zone as it is completed and inspected. Records actual parameters used (not just intended parameters), inspector identification, date, and time. Provides the structural engineering traceability that documents which zones were blasted at what energy level.<\/p>\n  <\/div>\n  <div class=\"pm-doc-card\">\n    <div class=\"dc-icon\">\ud83c\udf21\ufe0f<\/div>\n    <h4>Environmental Conditions Log<\/h4>\n    <p>Temperature and relative humidity at time of blast and at time of primer application. Both must be within the ranges specified in the maintenance manual. Documented by the operator at the beginning of each work shift and whenever environmental conditions change.<\/p>\n  <\/div>\n  <div class=\"pm-doc-card\">\n    <div class=\"dc-icon\">\ud83e\uddea<\/div>\n    <h4>NDI Inspection Records<\/h4>\n    <p>Results of Non-Destructive Inspection performed on bare structure after depaint \u2014 eddy current, fluorescent penetrant, or ultrasonic depending on the inspection requirement. NDI findings and dispositions become part of the aircraft&#8217;s permanent structural maintenance record.<\/p>\n  <\/div>\n  <div class=\"pm-doc-card\">\n    <div class=\"dc-icon\">\u267b\ufe0f<\/div>\n    <h4>Waste Characterization &amp; Disposal Records<\/h4>\n    <p>TCLP or other appropriate characterization of spent blast media mixed with stripped paint residue. Disposal manifest (EPA Uniform Hazardous Waste Manifest for hazardous waste). Retained for minimum 3 years per RCRA requirements; longer if state regulations require.<\/p>\n  <\/div>\n<\/div>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 15 \u2014 WASTE MANAGEMENT\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-waste\">Waste Management &amp; Environmental Compliance<\/h2>\n\n<p>Aerospace depaint waste management is one of the most complex environmental compliance challenges in aviation maintenance, driven by the presence of hexavalent chromium in stripped primer residue and the volume of waste generated in large-scale depot operations.<\/p>\n\n<h3>Waste Stream Characterization<\/h3>\n<p>Spent plastic blast media from aircraft depaint operations is a mixture of fractured media particles, stripped paint fragments, and primer residue. The hazardous waste classification of this mixture depends entirely on its chemical composition:<\/p>\n<ul>\n  <li><strong>Chromate primer residue (Cr\u2076\u207a):<\/strong> If the stripped coatings include MIL-PRF-23377 chromate primer, the waste must be tested by TCLP (Toxicity Characteristic Leaching Procedure) for chromium. If TCLP chromium concentration exceeds 5.0 mg\/L, the waste is classified as D007 Hazardous Waste under RCRA and must be managed accordingly \u2014 licensed transporter, licensed treatment\/disposal facility, EPA Uniform Hazardous Waste Manifest for each shipment.<\/li>\n  <li><strong>Non-chromate primer residue:<\/strong> Aircraft stripped of non-chromate primer systems only (newer coatings, or aircraft that have previously transitioned to non-chromate) produce waste that may be non-hazardous. Confirm with TCLP testing before assuming non-hazardous classification.<\/li>\n  <li><strong>Lead-containing primers:<\/strong> Some older aircraft carry lead-containing surfacers or primers. If lead is present, D008 (lead) hazardous waste classification also applies.<\/li>\n<\/ul>\n\n<h3>Air Emissions<\/h3>\n<p>Blast hangar ventilation systems must be designed to capture and filter blast dust to protect both operators and the surrounding environment. HEPA filtration or equivalent is typically required for hangar exhaust air when blasting chromate-coated aircraft. The concentration of hexavalent chromium in exhaust air must be maintained below the OSHA Permissible Exposure Limit (PEL) of 5 \u00b5g\/m\u00b3 as an 8-hour TWA for areas where operators are present, and below ambient air emission limits for the facility operating permit.<\/p>\n\n<h3>Pollution Prevention Hierarchy<\/h3>\n<p>The most cost-effective environmental strategy for aerospace depaint operations is chromate primer elimination at the source \u2014 transitioning aircraft paint systems to non-chromate primer equivalents. The U.S. Air Force and Navy have both ongoing programs to qualify and implement non-chromate primer systems across their fleets, which will progressively reduce the regulatory burden of waste management as aircraft cycle through repaints using the new systems. Until that transition is complete, rigorous waste management protocols remain mandatory for any facility performing depaint on chromate-coated aircraft.<\/p>\n\n<hr class=\"pm-section-divider\">\n\n\n<!-- \u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n     SECTION 16 \u2014 FAQ\n\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550 -->\n<h2 id=\"aero-faq\">\u0427\u0430\u0441\u0442\u043e \u0437\u0430\u0434\u0430\u0432\u0430\u0435\u043c\u044b\u0435 \u0432\u043e\u043f\u0440\u043e\u0441\u044b<\/h2>\n\n<div class=\"pm-faq\" itemscope itemtype=\"https:\/\/schema.org\/FAQPage\">\n\n  <div class=\"pm-faq-item\" itemscope itemprop=\"mainEntity\" itemtype=\"https:\/\/schema.org\/Question\">\n    <p class=\"pm-faq-q\" itemprop=\"name\">How many times can an aircraft be depainted with plastic media before cumulative effects become a concern?<\/p>\n    <div itemscope itemprop=\"acceptedAnswer\" itemtype=\"https:\/\/schema.org\/Answer\">\n      <p class=\"pm-faq-a\" itemprop=\"text\">The research consensus, based on multiple Air Force-funded studies, is that repeated plastic media blast cycles at qualified parameters do not produce cumulative fatigue life degradation \u2014 each blast cycle produces the same near-neutral residual stress state as the first, rather than incrementally worsening the surface condition. This finding is what makes plastic media blasting sustainable as a recurring maintenance process over the full service life of an aircraft. However, the conclusion depends entirely on maintaining parameters within the qualified process window on every cycle. An aircraft that has been over-blasted on even one cycle has an altered residual stress state that may not be visible on subsequent inspection but affects fatigue life accumulation. The practical answer is: there is no defined limit on the number of plastic media depaint cycles for aircraft maintained to process specification, but the process must be correctly executed on every cycle without exception.<\/p>\n    <\/div>\n  <\/div>\n\n  <div class=\"pm-faq-item\" itemscope itemprop=\"mainEntity\" itemtype=\"https:\/\/schema.org\/Question\">\n    <p class=\"pm-faq-q\" itemprop=\"name\">Does plastic media blasting remove the chromate conversion coating (Alodine) from aluminum?<\/p>\n    <div itemscope itemprop=\"acceptedAnswer\" itemtype=\"https:\/\/schema.org\/Answer\">\n      <p class=\"pm-faq-a\" itemprop=\"text\">Plastic media blasting does partially disturb or remove chromate conversion coating from aluminum surfaces. Conversion coating (Alodine\/Iridite per MIL-DTL-81706) is a very thin (0.01\u20130.05 mil) chemically bonded layer \u2014 it is not a free-standing film and does not delaminate the way paint does. However, the mechanical action of blast media does modify the conversion coating surface, reducing its visual intensity and potentially removing it in local areas. For this reason, aerospace maintenance procedures typically require touch-up application of conversion coating to any areas where the original coating has been disturbed before re-prime application. The conversion coating replenishment step is critical to the long-term corrosion protection of the repainted structure \u2014 omitting it leaves bare aluminum with only the organic primer as its corrosion barrier, significantly reducing corrosion performance compared to conversion coat + primer systems.<\/p>\n    <\/div>\n  <\/div>\n\n  <div class=\"pm-faq-item\" itemscope itemprop=\"mainEntity\" itemtype=\"https:\/\/schema.org\/Question\">\n    <p class=\"pm-faq-q\" itemprop=\"name\">Can plastic media blasting be performed on an aircraft that has not been fully disassembled?<\/p>\n    <div itemscope itemprop=\"acceptedAnswer\" itemtype=\"https:\/\/schema.org\/Answer\">\n      <p class=\"pm-faq-a\" itemprop=\"text\">Yes \u2014 most depot depaint operations are performed on aircraft that are largely assembled, with engines removed and systems powered down, but with structural assemblies (wings, stabilizers, fuselage) intact. The key requirements for blasting an assembled aircraft are comprehensive masking of all openings, sensors, and protected components per the applicable Technical Order masking diagram; complete engine inlet and exhaust blanking; removal of all flight surfaces that carry composite materials requiring different blast parameters; and post-blast inspection for media entrapment in any crevice, fastener hole, or system interface that could trap media. Media entrapment is particularly critical \u2014 trapped media in structural crevices or hydraulic fitting areas can cause corrosion damage significantly worse than the original stripped coating. A formal media entrapment inspection, using bright lighting and compressed air flushing of all potential entrapment locations, must be completed and documented before the aircraft returns to service.<\/p>\n    <\/div>\n  <\/div>\n\n  <div class=\"pm-faq-item\" itemscope itemprop=\"mainEntity\" itemtype=\"https:\/\/schema.org\/Question\">\n    <p class=\"pm-faq-q\" itemprop=\"name\">What is the minimum facility infrastructure needed to perform qualified aerospace depaint operations?<\/p>\n    <div itemscope itemprop=\"acceptedAnswer\" itemtype=\"https:\/\/schema.org\/Answer\">\n      <p class=\"pm-faq-a\" itemprop=\"text\">A minimum-capability aerospace depaint facility requires: an enclosed blast hangar of sufficient size to accommodate the largest aircraft to be worked (typically minimum 100 ft \u00d7 100 ft \u00d7 30 ft clear height for fighter\/attack aircraft; larger for transports); ventilation and dust collection rated for the hazardous materials in the waste stream; a media reclaim system (floor recovery, air wash separator, screen classification) sized for the expected media throughput; a compressor system capable of sustained delivery at nozzle pressure (typically 25\u2013100 HP rotary screw compressor); temperature and humidity control (or monitoring with work stoppage limits); HEPA filtration on exhaust air when blasting chromate-coated aircraft; hazardous waste accumulation area for spent media; and a quality system that supports the documentation requirements described above. For NADCAP-accredited facilities (required for Tier 1 aerospace contractors and many DoD depot operations), additional audit requirements apply to process documentation, operator qualification, and calibration systems.<\/p>\n    <\/div>\n  <\/div>\n\n  <div class=\"pm-faq-item\" itemscope itemprop=\"mainEntity\" itemtype=\"https:\/\/schema.org\/Question\">\n    <p class=\"pm-faq-q\" itemprop=\"name\">Is plastic media blasting approved for use on the Boeing 787 and Airbus A350?<\/p>\n    <div itemscope itemprop=\"acceptedAnswer\" itemtype=\"https:\/\/schema.org\/Answer\">\n      <p class=\"pm-faq-a\" itemprop=\"text\">Plastic media blasting is approved for use on both the 787 and A350, but with zone-specific media type requirements that reflect the composite-intensive construction of these aircraft. For metallic zones (aluminum frame elements, titanium fittings, certain door surrounds), standard Type II urea parameters apply per the respective Aircraft Maintenance Manual. For CFRP composite zones \u2014 which constitute approximately 50% of the structural surface on both types \u2014 Type V acrylic media is required, typically at Mesh 30\u201350 and pressures in the 20\u201335 PSI range. The 787 and A350 AMMs include specific depaint procedures and parameter tables for each structural zone. MRO facilities performing depaint work on these types must have their processes approved against the OEM-specified parameters and must use media that meets the specified requirements. The specific AMM section references should be obtained directly from Boeing or Airbus Customer Services \u2014 as living documents, AMMs are subject to revision, and the latest approved revision must be used.<\/p>\n    <\/div>\n  <\/div>\n\n<\/div>\n\n<hr class=\"pm-section-divider\">","protected":false},"excerpt":{"rendered":"<p>How Plastic Media Is Used in Aerospace Depainting Every commercial  [&#8230;]<\/p>","protected":false},"author":1,"featured_media":12330,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[62,177,138],"tags":[],"class_list":["post-12314","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","category-material","category-resource"],"_links":{"self":[{"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/posts\/12314","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/comments?post=12314"}],"version-history":[{"count":3,"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/posts\/12314\/revisions"}],"predecessor-version":[{"id":12403,"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/posts\/12314\/revisions\/12403"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/media\/12330"}],"wp:attachment":[{"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/media?parent=12314"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/categories?post=12314"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hlh-js.com\/ru\/wp-json\/wp\/v2\/tags?post=12314"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}