In the present study nanocrystalline Co-W coatings were deposited on the copper substrate at current densities within the range of 2.5-70 mA/cm 2 , at room temperature. The coatings showed good adhesion to the substrate. All coatings were single phase solid solution. It means that coatings were super saturation solid solution. At all current densities used, the grain size of coatings produced remained almost constant. It was seen that with increasing the current density, the tungsten content of coatings decreased. This is probably due to the low diffusion of tungsten ion complexes in the diffusion polarization region. These coatings showed spherical nodular stracture. By increasing the current density, the number of nodules and microcracks increased. The coatings produced at highest current density used (i. e. 70 mA/cm 2 ) showed the most corrosion resistance. This could be due to the lowest exchang current density of water reduction in the present of oxygen on these coatings. According to the cyclic polarization, these coatings are resistant against pitting corrosion in the present of ionic chloride. EIS results confirmed that the mechanism of tungsten co-deposition is changed with applied current density. Tungsten deposition proceeds via the reduction of tungsten oxide or adsorption and concequent reduction of complexes formed in the bulk of solution. At current density in the activation polarization region, the reduction of tungsten oxide by adsorbed hydrogen was dominated. By increasing the current densities in to the regions of mixed and diffusion polarization, the adsorption and reduction of tungsten containing ion complexes would be the controlling parameter. As it was observed, compared with tungsten content the effect of grain size on the microhardness of coatings was negligible. the highest microhardness value of about 640 vickers, belonged to the coatings produced at 2.5 mA/cm 2 . At this current density, the coatings produced had the maximum tungsten content and showed the most wear resistance.