AMS 2471
Anodic Treatment of Aluminum Alloys, Sulfuric Acid Process, Undyed Coating
Establishes processing and performance requirements for sealed, undyed sulfuric-acid anodic coatings on aluminum alloys.
What AMS 2471 specifies
AMS 2471 is the aerospace process specification for undyed sulfuric-acid anodizing of aluminum alloys. Unlike a decorative color specification, it controls process quality through appearance, unsealed coating weight, sealing, and corrosion resistance. The unsealed coating weight is at least 600 mg/ft² (6.5 g/m²), and qualification panels receive at least 336 hours of ASTM B117 salt spray. It does not establish a universal drawing thickness. Buyers should state significant surfaces, masking, contact locations, any dimensional limit, and whether a particular approved sealer is required.
Tests and the drawing call-out
Tests the document imposes
- Unsealed coating weight by ASTM B137, minimum 600 mg/ft² (6.5 g/m²)
- ASTM B117 salt spray for at least 336 h
- Visual examination for burning, powdering, discontinuity, and objectionable staining
- Process-solution and sealing control
How to cite it
Drawing call-out
ANODIZE PER AMS 2471, UNDYED, <THICKNESS IF REQUIRED>, <SEAL>, <MASKING>Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
Finishes specified to AMS 2471
AMS 2471 — frequently asked
Does AMS 2471 define a color?
It specifies an undyed anodic coating, so the natural appearance varies with alloy and pretreatment. If cosmetic consistency matters, approve a sample and state the allowed appearance range.
How thick is AMS 2471 anodize?
The specification controls a minimum unsealed coating weight of 600 mg/ft² but does not provide one universal drawing thickness. State a thickness separately when dimensions or wear performance depend on it.
What corrosion test applies?
Qualification panels are exposed for at least 336 hours under ASTM B117. Acceptance includes limits on isolated pits, so a buyer should not replace the full requirement with only an hour count.
AMS 2471 is copyrighted by SAE International. This page explains the document so a drawing can be read; it does not reproduce the standard. Purchase the current edition from the publisher. Official source ↗