Mechanically assisted electroplating of Ni–P coatings on carbon steel

Ni–P coatings on carbon steel were plated by a mechanically assisted electroplating technique, which combines the conventional electroplating technique with mechanical ball-rolling. The mechanical ball-rolling was conducted by vibrating the sample being plated with glass balls on it. For comparison, the conventional Ni–P electroplating technique without mechanical ball-rolling was also used to deposit Ni–P coatings under the same coating conditions as those adopted in the mechanically assisted electroplating. The experimental results show that the Ni–P coatings electroplated with mechanical assistance were smoother in surface, thinner in thickness, harder in hardness, more positive in corrosion potential, and greater in polarization resistance in comparison with the Ni–P coatings electroplated without mechanical assistance. The mechanical ball-rolling made the Ni–P coatings crystallized in-situ during the coating process, thereby avoiding crystallization-induced cracking, which was observed during the crystallization of the amorphous Ni–P coatings electroplated without mechanical assistance. A simple phase transformation model explains qualitatively the Ni–P in-situ crystallization during the mechanically assisted electroplating.