AEP-65 test method for paint systems resistant to chemical agents

What it is

AEP-65 is a NATO Allied Engineering Publication that defines a laboratory test method and fixed pass/fail criteria for paint systems meant to resist chemical agents on military equipment. It is a test protocol, not a paint specification: it tells a laboratory how to measure a candidate paint system's performance, not what the paint has to be made of.

A two-stage absorption and desorption test

The method contaminates a painted test panel with a chemical agent, then measures two things on the same sample: how much agent the paint absorbs in total, and how much of it desorbs onto a contact sampler, currently silica gel chosen as "representative as is practical of human skin" (clause 1.3), within fifteen minutes of contact. That fifteen-minute figure represents an operational touch, not a storage or handling limit.

Fixed pass/fail thresholds for three agents

Chapter 3 sets the acceptance criteria against three chemical agents, at an initial contamination density detailed in AEP-7 Chapter 6. For HD, the total absorbed quantity must be 60 μg/cm² or less and the quantity desorbed within 15 minutes 10 μg/cm² or less (Chapter 3). For VX and GD, the total absorbed quantity must each be 12 μg/cm² or less and the desorbed quantity 1 μg/cm² or less (Chapter 3). A laboratory reports a plain pass or fail against these thresholds for a specific paint system.

How it reaches a paint programme

AEP-65 is not itself a technical specification a supplier designs to from scratch; the specification it is usually invoked under is STANAG 4360, "Specification for Paint Systems, Resistant to Chemical Agents and Decontaminants for the Protection of Land Military Equipment." Ratifying STANAG 4360 automatically invokes AEP-65 (clause 1.2). Separately, the document says its own acceptance procedures and criteria "may be used by nations as a separate stand-alone requirement for paint systems" and are "not limited to joint NATO defence paint materiel projects which implement STANAG 4360" (clause 1.2), so a national programme can call up AEP-65's test on its own terms too. A tender or contract is where a supplier actually meets it, not the publication existing on NATO's own list.

What the test involves

Eighteen 50 x 50 x 1 mm test panels, aluminium alloy 5083 or 7020-T6, or steel, are painted to the manufacturer's instructions and to ISO 1514:2016, cured 24 hours then force-dried 10 days, and conditioned again on receipt at the test facility (clause 4.3). Panels are contaminated with HD, VX or GD within 150 seconds, held for 90 minutes, then decontaminated in ethanol within 30 seconds of that hold ending (Chapter 5). What follows is gas chromatography on two separate extractions, one from an adsorbent pressed onto the panel for 15 minutes (the desorbed quantity, Chapter 6) and one from the panel itself extracted repeatedly until negligible (the absorbed quantity, Chapter 7), each checked against a reference sample from an uncontaminated panel to rule out background interference from the paint formulation.

Where the method stops short

The document is candid about its own limit: the silica-gel contact sampler is a laboratory proxy, and several nations are still working to relate laboratory results to what an unprotected person actually accumulates from real "touches" of random frequency, duration and applied pressure (clause 1.3). AEP-65 expects to be revised again once that work matures enough to sharpen the pass/fail criteria.

Standards it references

• AEP-07Background
• AEP-58Background