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.
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