Improving the pitting corrosion resistance of aa1050 aluminum by removing intermetallic particles during conversion treatments

Abstract

Measurements of the open circuit potential of AA1050 were performed in 10mM CrO3, and the Al-matrix around the intermetallic particles was found to dissolve locally. Pre-immersion in 1M NaOH promoted the dissolution of the Al-matrix around intermetallic particles, resulting in the improvement of pitting corrosion resistance in NaCl solutions. The pitting corrosion resistance provided by molybdate treatment is effectively improved by pre-immersion in NaOH. The maximum pit depth of the specimen treated in MoO3HNO3 solution after preimmersion in 1M NaOH was small compared to the chromate-treated specimen. It was determined that immersion in an acidic solution containing an inhibitor after pre-immersion in NaOH is an effective method to improve the pitting corrosion resistance of aluminum alloys.