Mil-A-8625, Anodize, (Aluminum)
Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. Aluminum is ideally suited to anodizing, although other nonferrous metals, such as magnesium and titanium, also can be anodized.
Anodizing increases corrosion resistance and wear resistance, and provides better adhesion for paint primers and glues than does bare metal. Anodic films can also be used for a number of cosmetic effects, either with thick porous coatings that can absorb dyes or with thin transparent coatings that add interference effects to reflected light.
Anodizing is also used to prevent galling of threaded components and to make dielectric films for electrolytic capacitors . Anodic films are most commonly applied to protect aluminium alloys , although processes also exist for titanium , zinc , magnesium , niobium , zirconium , hafnium , and tantalum . Iron or carbon steel metal exfoliates when oxidized under neutral or alkaline microelectrolytic conditions; i.e., the iron oxide (actually ferric hydroxide or hydrated iron oxide , also known as rust ) forms by anoxic anodic pits and large cathodic surface, these pits concentrate anions such as sulfate and chloride accelerating the underlying metal to corrosion.
The color of the finished anodized product can vary in color. The AAC Color Standards detail the specific testing procedures for anodic coating thickness, coating density and seal integrity. These properties can be checked by the appropriate ASTM B244, ASTM B137, ASTM B680, ISO 2360, or ISO 3210. The following are similar or carried under Mil-A-8625F.
AMS-2468E Hard coat 0.002" AMS-2469D Hard coat 0.002".
AMS-2470H Chromic acid process.
AMS-2471D Sulfuric acid process - no dye coating.
AMS-2482A Hard coat 0.002" with Teflon.