Scanning electrochemical microscope study on pitting corrosion of iron

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 mum 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 mum 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.