Effect of Surface Preparation on Corrosion Resistance of Electrochemically Deposited Ni-Mo Alloys in the Presence 1-Methyl-Imidazolium Chloride Ionic Liquid

Abstract

Electrodeposition of Ni-Mo was successfully carried out in the presence of 1-methyl-imidazolium chloride as an additive using ammonia-citrate bath. To investigate the effect of substrate preparation on corrosion resistance; the corrosion resistance of NiMo coatings deposited on mild steel substrate, that was electropolished or mechanically polished, have been compared in 3.5 wt.% NaCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy. The structural properties of Ni-Mo were evaluated using X-ray diffraction and their morphology, microstructure and chemical composition were also investigated using scanning electron microscopy and X-ray energy dispersive spectroscopy. Temperature and pH of the bath have been also changed in order to investigate their effects on corrosion resistance. The results showed that, the Ni-Mo deposited onto electropolished substrates were more resistant to corrosion than on mechanically polished ones; and ionic liquid leads to increase the corrosion resistance of coatings at pH of 8.5, but decreases the corrosion resistance of coatings deposited at pH of 9.5.