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

•Multiscale electrochemical characterization of sol-gel coatings on AA2024-T3.•Inhibitor efficiency screening using electrochemical microscopy.•Chemical sensitive imaging assists to identify the action of additive in the coating.•Piperazine addition originates an insulating silane layer that inhibits charge transfer.

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.

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