Time-lapse potentiometric imaging of active filiform corrosion using a scanning Kelvin probe technique

摘要

The kinetics and mechanism of filiform corrosion occurring on polymer coated AA2024-T3 aluminium alloy areninvestigated using a scanning Kelvin probe technique (SKPT). Repeated scanning by SKPT is used to generatena time-lapse animation showing the dynamic evolution of localised free corrosion potential (Ecorr) patterns.nEcorr values in the head region of propagating filaments are up to 150 mV lower that the intact polymer coatednsurface, indicating local depassivation. However, Ecorr values in the filament tail are ca. 100 mV higher thannbackground, indicating superpassivation. Spatial analysis of instantaneous Ecorr distributions indicates thatnanodic metal dissolution is concentrated at the leading edge, and cathodic oxygen reduction at the trailing edge,nof active filament heads. Temporal analysis of time-dependent Ecorr distributions shows that filamentsnpropagate at a constant speed and do not intersect.