This specification establishes the for anodic coatings on aluminum alloys. This process has been used typically to increase corrosion resistance and to provide surfaces which will promote adherence of paint and other organic finishes, and has been found useful for assemblies which have faying surfaces and/or which may trap electrolyte, but usage is not limited to such applications. This process is primarily applicable to aluminum and aluminum alloy parts which have nominal copper content not greater than 5% by weight or total nominal alloy content not greater than 7.5% by weight, AMS 2471 being recommended for parts having higher alloy content. Coating may