Electrochemical investigation of corrosion and repassivation of structural aluminum alloys under permanent load in bending

This work reports an electrochemical investiga- tion of corrosion and repassivation in NaCl solutions of structural Al 7075-T6 and Al 2024-T3 as a function of per- manent load in bending by means of single-cycle anodic polarization. Experimental variables other than the load level were the extent of corrosion, chloride ion concentra- tion and initial pH of the test solution, in addition to the pre-exposure in the aggressive environment and of the vis- cosity of the test solution for Al 7075-T6. The susceptibility to local stress during corrosion and repassivation depends on the alloy microstructure and corrosion mechanisms. In the case of Al 2024-T3, the mechanical activation is driven by cathodically controlled dissolution of this alloy at open circuit in concentrated NaCl, being indicative of a chemo- mechanical effect. Conversely, for Al 7075-T6, the effect of applied load is better discerned from the repassivation response. Film rupture/formation sequence and related interfacial (electro)chemical processes determine the stress-enhanced metastable repassivation of this alloy.