Abstract
Ni-P electroplating is widly used as a corrosion prevention technique, but the fact that the high corrosion resistance of Ni-P film is due to its amorphous structure is not well known. A detailed investingation was therefore conducted on the process by which the film become amorphous as more and more P is added. Electroplated Ni film is crystalline, with a prefered orientation of 220. When 5 at % P is mixed into this Ni film, the orientation is changed to 111 and the crystals in the film assume an elliptical or columnular shape about 50Å in diameter and 100Å or less in length, perpendicular to the surface of the film. When the concentration of P reaches about 10 at%, the crystals assume a needle shape, and at higher P concentrations, the needle length decreases and the film becomes amorphous. It is concluded that the direct cause of the amorphous structure of the film is P concentration, not multiple nucleation. It further seems that the amorphous formation is related to the adsoption of P atoms to Ni atom and to the obstruction of nucleation and grain growth-What we term the theory of obstruction of nucleation or obstruction of grain growth.
