Corrosion Protection of Al Alloys and Al-Based Metal Matrix Composites by Chemical Passivation
- 1 August 1989
- journal article
- Published by Association for Materials Protection and Performance (AMPP) in Corrosion
- Vol. 45 (8) , 615-630
- https://doi.org/10.5006/1.3579314
Abstract
Chemical passivation by immersion of Al alloys and Al 6061/SiC and Al 6061 /graphite metal matrix composites in a CeCl3 solution produces very corrosion-resistant surfaces. Al 6061 and Al 7075-T6 that had been immersed in 1000 ppm CeCl3 for one week did not suffer from pitting corrosion during immersion in aerated 0.5 N NaCl for three weeks. For Al 7075-T73 some improvement of the corrosion resistance was also achieved, but to a much lesser extent. Chemical passivation in CeCl3 was also successful for Al/SiC and Al/graphite. A comparison with the improvements of the corrosion resistance of Al alloy by treatment with chromate conversion coatings shows that chemical passivation provides a valuable alternative to this process. The passivation process in CeCl3 and the corrosion process in NaCl have been monitored continuously with electrochemical impedance spectroscopy (EIS), which has been shown to be a very sensitive technique for the evaluation of these reactions. Pitting can be detected by the oc...Keywords
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