MIL-A-8625F, MILITARY SPECIFICATION: ANODIC COATINGS FOR ALUMINUM AND ALUMINUM ALLOYS (10 SEP 1993)., This specification covers the requirements for six types and two classes of electrolytically formed anodic coatings on aluminum and aluminum alloys for non-architectural applications
Hard anodizing is a term used to describe anodic coatings with surface hardness and/or abrasion resistance as their primary characteristic. Great for surface to surface sliding with low loads The color of the natural anodic coating depends on the alloy and the coating thickness. e.g. 6061 has a tan or gray color which darkens to almost black at .003"; 6063 has an amber shade which darkens to bronze. Both are considered clear. After hard anodizing surfaces may be sealed in boiling distilled water, sodium dichromate solution, dewatering oil, wax or PTFE solutions
Class 1: Not dyed or pigmented.
Class 2: Dyed. (Specify color on Drawing).