Influence of titanium or aluminum doping on the electrochemical properties of CrN coatings in artificial seawater

CrN, CrTiN and CrAlN coatings were deposited on Si (100) via co-sputtering chromium, titanium and aluminum targets by using unbalanced magnetron sputtering, respectively. And the relevant microstructure and composition were characterized. The influences of the doping elements on the microstructural and electrochemical properties of CrN coatings in the artificial seawater were analyzed via the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests. As a result, the CrN coating exhibits the favorable corrosion resistance. On the contrary, the easy occurrence of hydration reaction for AlN would lower the compactness of CrAlN, subsequently deteriorate its corrosion resistance. Thus, the CrAlN coating presents the worst electrochemical properties in spite of its highest electrical resistivity. In particular, the CrTiN coating exhibits the outstanding corrosion resistance with relatively higher charge transfer resistance (Rct), polarization resistance (RP) due to its great compactness.