Scanning electrochemical microscopy measurement of ferrous ion fluxes during localized corrosion of steel

Local fluxes of ferrous ions at low carbon steel surfaces coated with tin and an epoxy-phenolic resin on tinplate samples, and at chrome steel (tin-free steel) have been monitored by oxidation of Fe2+ ions at the tip of a Pt scanning electrochemical microscope (SECM). The samples were immersed in 10 mM H2SO4 in order to avoid Fe(OH)3 precipitation. The SECM was employed in the collection mode at constant height (≈10–15 μm) on an x–y plane above the sample, monitoring the tip current as a function of tip location.