An Alternative to Chromic Acid Anodizing

Replacement of chromium containing materials and processes is the focus of extensive research and development activity due to increasingly stringent environmental regulations stemming from hexavalent chromium toxicity concerns. This, in turn, has increased the cost of hardware manufacture.

This paper describes the efforts of Boeing Commercial Airplanes in developing a more environmentally suitable alternative process to chromic acid anodizing. Several alternative processes were evaluated prior to selection of a boric-sulfuric acid anodize (BSAA) process. Results of screening tests (including corrosion resistance, paint adhesion, abrasion resistance and fatigue life) and subsequent BSAA process optimization are included.