Corrosion resistance for anodized parts having convex surface features

Abstract

Anodic oxide coatings that provide corrosion resistance to parts having protruding features, such as edges, corners and convex-shaped features, are described. According to some embodiments, the anodic oxide coatings include an inner porous layer and an outer porous layer. The inner layer is adjacent to an underlying metal substrate and is formed under compressive stress anodizing conditions that allow the inner porous layer to be formed generally crack-free. In this way, the inner porous layer acts as a barrier that prevents water or other corrosion-inducing agents from reaching the underlying metal substrate. The outer porous layer can be thicker and harder than the inner porous layer, thereby increasing the overall hardness of the anodic oxide coating.