An Investigation of Corrosion, Pitting Corrosion and Wear Behaviour of Nanocrystalline Co-W Coating Obtained by Direct Current

In the present study nanocrystalline Co-W coating was deposited on copper substrate at different current densities. All coatings were single phase solid solution with constant grain size. These coatings showed spherical nodular structure. By increasing the current density, the number of nodules and microcracks increased. The coating produced at higher current density showed more corrosion resistance. This could be due to the lower exchange current density of water reduction in the present of oxygen on this coating. According to cyclic polarization in 3.5% NaCl solution, these coatings were resistant against pitting corrosion in the present of ionic chloride. It was seen that by increasing the current density, the tungsten content of coating decreased. This is probably due to the low diffusion of tungsten ion complexes. It was assumed that lower microhardness and wear resistance was related to lower tungsten content at higher current densities.