Scanning microelectrochemical characterization of the effect of polarization on the localized corrosion of 304 stainless steel in chloride solution

•Microelectrochemical characterization of the effect of polarization on the localized corrosion of 304 stainless steel.•Spatially-resolved detection of local release of Fe(II) ions, and their conversion to Fe(III), as function of polarization.•Susceptibility to localized corrosion influenced by surface modification of the surface.•Onset of anodic local dissolution monitored by SVET as function of acidity and chloride ion concentration.

Corrosion processes occurring on stainless steel 304 surfaces under anodic polarization were characterized using scanning electrochemical microscopy (SECM) and the scanning vibrating electrode technique (SVET), complemented with conventional potentiodynamic polarization curves. Stable pit formation on the samples was monitored by SVET as result of surface modification under electrochemical control. The operation procedure may involve the previous electrochemical reduction of the passive oxide layer if the media is not aggressive enough to induce pitting at small overpotentials. Additionally, the sample generation – tip collection operation mode of the SECM enabled to detect local release of iron (II) ions, as well as their conversion to iron (III), both processes being greatly affected by the potential applied to the substrate.

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