Galvanic Corrosion - Anodized and Alodized Aluminum Coupled with 347 Cres and 6Al-4V Titanium

摘要

Aluminum panels (20424-T3), chromic and sulfuric acid anodized and alodized (chromate treated), were coupled with strips of 6Al-4V titanium and 347 CRES and subjected to salt-spray testing. Anodized panels were exposed for 240 hours and alodized panels for 160 hours. Sulfuric acid anodizing afforded the best protection and there was no observed galvanic corrosion. Chromic acid anodizing exhibited slight galvanic corrosion against titanium, but more significant corrosion against 347 CRES. The alodized panels exhibited heavy galvanic corrosion against both titanium and 347 CRES. Sulfuric acid anodized coatings should be used against 347 CRES, while either sulfuric acid or chromic acid anodized coatings are satisfactory against 6Al-4V titanium. Chromate conversion coatings should not be used as a final coating when dissimilar metallic coatings cannot be avoided. (Author)