Study of crucial factors for minimizing the roughness of chemical coatings with Ni – P and Ni – Cu – P alloys

The surface roughness of coatings has a significant impact on their functional properties and efficiency. We present the results of studying the effect of the main technological parameters on the roughness of chemical coatings with Ni – P and Ni – Cu – P alloys. The key factors affecting the roughness of coatings were determined by the Taguchi method. Parameters of the coating process were varied in the experiments: concentration of components in solution, pH, temperature, and the time of deposition. It is found that the surface roughness increases linearly with the thickness of coatings. The concentration of sodium hypophosphite and pH value have the greatest influence on the development of roughness. It is shown that the lowest roughness is observed at concentrations of sodium hypophosphite and copper salt 0.358 and 0.0012 mol/liter, pH 5.8 and temperature 90 °C. The rate of the surface roughness development for Ni – P and Ni – Cu – P coatings under optimal conditions is 0.68 and 0.97 %/μm (before optimization — 6.72 %/μm). The obtained results can be used to improve the methodology for reducing the roughness of coatings with Ni – P and Ni – Cu – P alloys and, accordingly, to improve the functionality, wear resistance and quality of coatings.