An investigation over the effect of the reducing agent on the properties of the ZnO-reinforced Ni–P coatings

Electroless ZnO-reinforced Ni–P coatings are developed on mild steel substrates in the Electroless bath, which contains an optimum concentration of ZnO nanoparticles. This work focuses on the characteristics and properties of the Ni–P–ZnO coatings developed at different concentrations of reducing agent (sodium hypophosphite). Results confirm that the reducing agent greatly influences the deposition rate, surface roughness, hardness, and corrosion resistance of the coating. Reducing agent concentration influences the phosphorus present in the coating. An increase in the amorphous nature of the coating with an increase in reducing agent concentration improves the resistance to corrosion of the coating, but at the same time, it decreases the microhardness of the coating. High phosphorus deposition at the maximum amount of reducing agent concentration lowers the microhardness of the coating. The Hard Ni3P crystalline phase formed at 400 °C enhances the resistance to corrosion and microhardness of the coating. Scanning electron microscopy and X-ray diffraction studies are used to characterize the Ni–P–ZnO coating. The microhardness and corrosion resistance of the coating were evaluated using a Vickers microhardness tester and potentiodynamic polarization studies.