Effect of rare earth addition on structure and properties of Ni-P coating on SiCp/Al composites

The aim of this work was to improve the properties of Ni-P coating on SiCp/Al composites. The effect of rare earths addition on Ni-P coating structure was investigated by means of scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD) and electrochemistry methods. The results showed that as Y or La concentration was 0.15 g/L in plating solution, the highest value of deposition rate of Ni-P coating was found. And the structure of the obtained coating was modified to part of crystalline state from single amorphous Ni, such as Ni3Y or Ni3La, Ni5Y or Ni5La, Ni2P2Y or Ni2P2La. The properties of the Ni-P-RE alloy coating were improved greatly, for example, crystalline size became fine and compact, the free corrosion potential of the coating enhanced remarkably. Y had a better effect on the properties of the coating compared with La.