Change of n-type to p-type conductivity of the semiconductor passive film on N-steel: Enhancement of the pitting corrosion resistance

Abstract

The electrochemically-assisted modification of the N-austenitic stainless steel (ASS N25) surface was successfully employed to improve barrier properties of the passive film in a chloride containing solution. The chemical composition, electronic and barrier properties of the surface film before and after the electrochemical treatment were examined using X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Electrochemical measurements were carried out in a corrosion testing solution. The excellent corrosion resistance (both pitting and general) of the N-steel’s modified surface was discussed according to the Mott-Schottky analysis of the interfacial capacitance of the space charge layer and EIS results. The conductivity change of the surface film from an n- to a p-type in the pitting susceptible region was explained using the XPS analysis and semiconducting properties of the film.

Keywords

• stainless steel
• corrosion
• passive films
• metal-oxide semiconductors