Corrosion protection of AA6061 T6 10% Al2O3 composite by molybdate conversion coatings

The corrosion protection performance of aluminum composite materials was investigated in 3.5% NaCl solution for time ranging between 1-60 days. Series of specimens were treated in molybdate solutions under different conditions. Free immersion and electrochemical activation techniques were used to apply the molybdate layer. The specimens which were directly treated or pickled before molybdate treatment showed severe pitting corrosion. Conversely, the specimens which were subjected to an oxide thickening step before the molybdate treatment showed outstanding corrosion protection. XPS revealed a higher amount of molybdate as MoO4 2- for the specimens prepared by electrochemical activation technique than for the free immersion technique.