Fabrication and characterization of bimetallic nickel-molybdenum nano-coatings for mild steel corrosion protection in 3.5% NaCl solution

Abstract

In this study, Ni-Mo alloy films with different weight ratios were coated on mild steel (G10700) by a novel and effective co-sputtering method, and their corrosion protection was investigated in 3.5 % NaCl solution. In the sputtering process, Ni and Mo targets were mounted at DC and RF sputtering guns, respectively. By introducing the sputtering gas (argon), bimetallic films were prepared under changing the power at the RF gun and keeping the current constant at the DC gun of the magnetron sputtering system. The coatings were characterized by different methods and their corrosion resistance in 3.5 % NaCl solution was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). The results of corrosion testing revealed that there is a relation between roughness and corrosion resistance, and all of the coatings (mono and bimetallic) have a protective effect, however, the highest performance was obtained at bimetallic coatings which the best composition was for the Mo-to-Ni weight ratio of 4.5 and 0.15 for 2 min and 1-week exposure time to the corrosive solution, respectively.