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AEP-61
Paint manufacturers and shipyards specifying or qualifying an underwater hull coating system for NATO-relevant vessels
NATO's test methods and acceptance criteria for qualifying underwater hull paint systems, covering corrosion and biofouling protection on ships' hulls.
AEP-61 is the NATO Allied Engineering Publication that sets out how an underwater hull paint system (UHPS) is qualified. It is a paint manufacturer's specification, not a company's: the document addresses the manufacturer who submits a coating system for testing and the navy "qualifying activity" that runs the test programme and decides whether the system qualifies. A UHPS in this document means the anticorrosive base coat or coats applied to the hull, an optional tie-coat, and the antifouling topcoat that resists marine biofouling such as barnacles and tubeworms.
The document fixes two service-life targets. Anticorrosive protection has to run at least 15 years in seawater-immersion corrosion category Im2 of ISO 12944-2. Antifouling protection is banded into short-life (2-3 years), intermediate-life (4-7 years) or long-life (8-12 years) classes, chosen according to the vessel's operating rate and speed profile. Within that service life, general topcoat re-application and localized repair are treated as ordinary minor maintenance rather than a failure of the system.
Basic product requirements follow from those targets. The anticorrosive coating has to use two or more coats, in colours distinguishable from each other and from the antifouling topcoat, at a minimum nominal dry film thickness of 250 micrometres excluding any zinc-rich primer or tie-coat. Application conditions are fixed at 85% relative humidity or below, a substrate temperature at least 3°C above the dew point, and an application temperature between 5°C and 35°C. Shelf life has to be at least 18 months for the anticorrosive paint and 12 months for the antifouling paint, and the system has to demonstrate cathodic-protection compatibility.
Qualification runs through laboratory tests, natural-exposure tests, and ship trials, each set out in a table with its own duration and standard. Laboratory work includes 1,440 hours of salt spray, 720 hours of water condensation, 4,200 hours of sea-water immersion, re-coatability and repairability testing, and six months of cathodic-protection compatibility testing against an initial 6 mm holiday. Natural-exposure testing immerses panels for one to several years depending on the antifouling type and the service-life class being sought. Ship trials move from hull patches, at least 2 metres wide and run for two to five years depending on vessel type and service-life class, to full-hull application. For trials on non-navy vessels, the document requires the work to be certified and verified by an independent third party the navy activity and the manufacturer agree on together.
Each test carries a numeric pass mark. Pull-off adhesion after exposure has to retain 50% of its original value with no adhesive failure, against thresholds of 4 MPa (or 3 MPa where the system uses a zinc-rich primer) before testing. Scribe-line delamination has to stay under 3 millimetres. No rusting, blistering, cracking or peeling is permitted after most tests. Biofouling acceptance depends on the antifouling type: under 10% colonised surface for static immersion, no more than 25% fouled area for dynamic-flow exposure, and 5% (or 15% for non-biocide systems) fouled area after a ship trial's high-pressure fresh-water wash. Cathodic disbondment has to produce a holiday diameter under 20 millimetres. Each component paint is also identified against a fixed schedule of physicochemical tests: density, solids content, pigment content, drying time, flash point, pot life, VOC content, and biocide release rate and content.
AEP-61 states plainly that application of paint containing tributyltin (TBT) "is now banned internationally", and that vessels already carrying TBT-containing antifouling coatings would need those coatings removed or sealed by the end of 2007. Separately, its environmental-impact requirements for qualification state that organotin biocides "are prohibited from use as antifouling agents" in the antifouling paint submitted. Antifouling paints are classified by biocide content into four bands, from high-release-rate copper systems through to biocide-free systems, and by mechanism into ablative/self-polishing, diffusion, or non-releasing types. Beyond these classifications and the organotin ban, the document does not set its own numeric limit on biocide release rate; where a release rate matters, it is a value the manufacturer reports against ISO 15181, not a threshold AEP-61 sets.
AEP-61 states that a UHPS qualified under it is intended to be applied in accordance with AEP-59 (Application Process for Optimum Paint and Coating Systems' Performance) to reach its intended service life: AEP-61 sets the qualification bar for the paint system, AEP-59 governs how it is applied. The specification is covered by STANAG 4698, which is the agreement by which NATO nations commit to it. Its normative references also draw in around fifty ISO and ASTM test methods, among them ISO 12944 (corrosion protection of steel structures), ISO 20340 (offshore protective paint systems), ISO 4624 (pull-off adhesion), ISO 4628 (coating degradation assessment) and ASTM D 6990 (biofouling resistance).
The document sets no NATO-wide qualified-products list, accreditation scheme or certificate: it describes a navy qualifying activity's own test-and-decide process, not a body that certifies against it. It sets no obligation of its own on who has to use it or when; that is a matter for whatever tender, contract or national implementation invokes it.
The work AEP-61 describes - preparing test panels, running salt-spray and cathodic-protection testing, coordinating ship trials, applying and repairing coatings on an actual hull - happens in a laboratory, a shipyard or on a vessel, not in software. ComplyTrain does not run that testing, and it does not decide whether a paint system qualifies; that stays with the navy qualifying activity and whatever independent third party it agrees with the manufacturer.
What ComplyTrain supports is the documentation trail around that work: the technical data sheets and product information a manufacturer has to submit for qualification, the test reports Chapter 9 requires (test laboratory, dates, panel preparation, before- and after-test assessments, any deviation from the test methods), training records for people applying or inspecting a qualified system, and an audit trail that ties a given test result back to the acceptance criteria it was measured against.
Which parts of a contract's quality clause apply to a given programme, and which standards sit alongside AEP-61 in it, is set by the contract itself. Our standards explorer shows what else is in the same family. If you want to talk through how a defence programme's documentation and training records are organised, get in touch.
Tell us how you need to work with AEP-61 and what you need from it. We will come back to you about what ComplyTrain can do.
Thank you. Your list is on its way to your inbox, and we will come back to you on what working with these standards in ComplyTrain involves, usually within one business day.
AEP-61 does not say so itself. It is covered by STANAG 4698, which is how NATO nations commit to the specification; whether a particular paint manufacturer has to meet it depends on the shipbuilding or navy contract that calls for a qualified underwater hull paint system.
AEP-61 sets the qualification tests and acceptance criteria a paint system has to pass. AEP-59 governs the application process for putting a qualified system onto a hull. AEP-61 states that a system qualified under it is intended to be applied in accordance with AEP-59 to reach its intended service life.
Yes, as the document itself states it: TBT application "is now banned internationally", and vessels already coated with TBT-containing antifouling paint needed those coatings removed or sealed by the end of 2007. Separately, organotin biocides generally "are prohibited from use as antifouling agents" in paint submitted for qualification under this AEP.
The document names a navy "qualifying activity" that administers the test programme in Chapter 7 and judges the results against the acceptance criteria in Table 7-2. For ship-trial patch and full-hull testing on non-navy vessels, it also requires certification and verification by an independent third party the navy activity and the manufacturer agree on together. AEP-61 names no NATO-wide certificate or accreditation body.
Individual laboratory tests run from 720 hours (water condensation) to 4,200 hours (sea-water immersion), and cathodic-protection compatibility testing runs six months. Ship trials run longer still: hull-patch testing runs two to five years and full-hull testing a similar span, depending on vessel type and the antifouling service-life class being sought.
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