Evolution of corrosion resistance and passive film properties of Ni-Mo alloy coatings during exposure to 0.5 M NaCl solution

The corrosion properties of Ni-Mo alloy coatings with different molybdenum content (11-32 wt%) were investigated in the course of exposure to 0.5 M NaCI solution. Polarization resistance and impedance measurements showed that after contact with corrosive media, the formation of passive film on the coating surface, determines the corrosion resistance of Ni-Mo alloys. XPS analysis revealed that, the passive film growth was enhanced by the presence of higher amounts (26-28 wt%) of Mo in the coating. It was found, that after exposure to corrosive solution, Mo oxides occurred at the passive film/metal interface, while Ni hydroxide dominated in the bulk of the passive film. (C) 2017 Elsevier B.V. All rights reserved.