Electrochemical and Exfoliation Corrosion Behavior of Reversion-Treated High-Strength Aluminum Alloy

Abstract

The present study aims to understand the microstructural modification affecting the electrochemical and exfoliation corrosion (EXCO) characteristics of aluminum alloy 7010. The alloy was aged for two different tempers, namely peak aging (T6) and retrogression and re-aging (RRA). The standard electrochemical polarization tests and EXCO tests were performed on the treated alloys. The microstructure of the alloy observed under a scanning transmission electron microscope revealed the presence of continuous grain boundary precipitates in T6 alloy. These precipitates were formed discontinuously after RRA treatment. The RRA alloy microstructure resulted in a shift toward positive potential. The exfoliation corrosion depth was reduced to 60–70 μm after RRA treatment, which was measured to be about 250 μm in T6 condition. The resistance toward the exfoliation corrosion was found to be influenced by the enriched Cu content of precipitates on grain boundary after reversion treatment. The results confirm that the RRA-tempered alloy improves both electrochemical corrosion and EXCO resistance. © 2020, The Indian Institute of Metals - IIM.