Modification of the corrosion response of steel substrates by ion-nitriding

This paper concentrates on the electrochemical behaviour of ion-nitrided coatings produced by cathodic arc plasma deposition. The corrosion of five different steel grades modified by ion-nitriding was investigated through electrochemical polarization and electrochemical impedance spectroscopy techniques in immersion tests performed in a 0.5 M NaCl solution. Ion-nitrided and bare steel substrates were employed. Enhanced corrosion resistance is found for the coated steels. A porous film is produced on the metallic substrates, which allows for electrochemical reactive areas to be developed inside the pores. Surface film breakdown results in the localised corrosion of the materials at potentials positive to the corresponding pitting potential values for each material in the testing solutio