Role of acidic chemistries in steam treatment of aluminium alloys

The effect of acidic chemistry on the accelerated growth of oxide on aluminium alloys Peraluman 706™ and AA6060 under exposure to high temperature steam was investigated. Studied chemistries were based on citrates and phosphates. Results showed that the presence of citrate and phosphate anions initiated oxide growth at the intermetallic particles while growth and corrosion performance of oxide was found to be a function of anions type and their concentration. Further, steam treatment with phosphates exhibited better performance under acetic acid salt spray and filiform corrosion test whereas delay in powder coating resulted in 1.5-3 times inferior performance.