Electrochemical and surface studies on the passivity of nitrogen and molybdenum containing laser cladded alloys in 3.5 wt% NaCl solution

Abstract

The electrochemical behavior of the laser cladded nitrogen and/or molybdenum containing alloys were studied in a 3.5 wt% NaCl solution at pH 4. Potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) measurements were performed to evaluate the corrosion resistance of the laser cladded alloys. The surface of the alloys, after the EIS measurements, were characterized with Auger electron microscopy and X-ray photo-electron spectroscopy. The results, as determined from potentiodynamic polarization tests, showed that the nitrogen containing alloys exhibited a lower passive current density and a higher resistance to pitting corrosion, when compared with those of the nitrogen free alloy. Passive film resistance, as determined from EIS measurements, of the nitrogen and molybdenum containing alloys, was higher than that of the nitrogen containing and molybdenum free alloy. The effects of the alloying elements of alloys in connection with the anodic polarization behavior, the passive film resistance and the chemical composition of the passive film are discussed.