ABSTRACT
This chapter describes the phosphoric acid anodize process that was originally developed for use with 250°F curing primers that are compatible with 250°F curing adhesive films, since these were the systems around which most of commercial aircraft problems centered. The different forms of aluminum that can be phosphoric acid anodized will usually play a minor role in the nature of the oxide produced during anodizing. Immersion tanks used for anodize rinse should be used for anodize rinse only. The anodic coating should be continuous, smooth, uniform in appearance, and free from discontinuities such as scratches, breaks, and areas that are not anodized when examined visually. The preprocess variables relate to the aluminum materials and their condition as they would arrive at the anodize process line. The wet processing steps, from alkaline cleaning through drying after phosphoric acid anodizing, should be performed in one continuous, uninterrupted sequence of processes, with the parts not drying at any time until the oven drying after phosphoric acid anodizing.
