Scanning Electrochemical Microscope Study on Pitting Corrosion of Iron

Abstract

Scanning Electrochemical Microscope (SECM) has been applied to study pitting corrosion of iron in a 50 mM NaCl solution at pH 8.4. In order to monitor pitting propagation, a platinum wire of 10 μm in diameter sealed in Pyrex glass tube was used as an ultra micro probe (tip electrode). In order to detect Fe³⁺ ion flux emitted from a pit mouth, the tip electrode was placed 5 μm above the pit and polarized at −0.4 V vs. Ag/AgCl/3 M KCl reference electrode so that the Fe³⁺ ion is reduced to Fe²⁺ on the surface. The Fe³⁺ ion was successfully detected on the tip electrode surface.