Scanning electrochemical microscopy characterization of sol-gel coatings applied on AA2024-T3 substrate for corrosion protection

Scanning electrochemical microscopy was employed to characterize the local surface activity of an AA2024-T3 coated with sol-gel. Corrosion inhibitors were added to the sol-gel either as soluble chemical species, namely 1,2,3-benzotriazole, Na⿿(diethyl(dithiocarbamate)), and piperazine, or using Ce(III)-montmorillonite containers. The Scanning electrochemical microscopy was operated in the feedback mode by using ferrocene-methanol as redox mediator. This experimental procedure allowed evaluation of the coating behaviour in damaged and non-damaged areas from the analysis of Z⿿approach curves and 2D maps. The results evidence differences in the local electrochemical activity of the modified coatings that correlate well with averaging electrochemical measurements using electrochemical impedance spectroscopy.