The induced co-deposition of Ni–Mo–W ternary alloy; Coatings for hardness and corrosion resistance applications

Abstract

Ni–Mo–W ternary alloy coatings were electrodeposited on mild steel substrate using citrate electrolyte for hardness and corrosion resistance applications. The influences electrolyte pH, electrolyte temperature and sodium molybdate concentrations on deposit qualities were studied. The sodium molybdate concentrations were varied from 0.025 to 0.1 M for obtaining alloy coatings with various molybdenum (Mo) compositions. The deposition condition such as electrolyte concentration, pH and temperature were optimized for obtaining good aesthetic (bright) appearance, surface stability and microhardness properties. The maximum Mo composition (47.71 wt %) in alloy deposit was achieved is 47.71 wt % using 0.1 M sodium molybdate concentration. The microhardness properties were increased from 850 HV to 946 HV by introducing molybdenum (47.71 wt %) as third alloying element in to Ni–W alloy matrix. The obtained mechanical and corrosion resistance properties of these ternary alloy coatings were compared with binary alloy and metallic coatings viz., Ni–W and Ni–Mo and metallic Ni coatings. The superior corrosion rate was observed for Ni–Mo–W alloy deposits (5.8 mpy) compared to Ni–W (9.04 mpy) and Ni–Mo (8.89 mpy) alloy.