ピロリン酸カリウム‐ホウ化水素カリウム系の無電解ニッケルめっき浴の電気化学的挙動

Abstract

The polarization behavior of nickel has been studied in the electroless nickel plating baths. The baths consisted of 0.2mol/l of potassium pyrophosphate and various concentrations of nickel chloride and potassium borohydride. The rate of electroless plating of nickel was also estimated by three electrochemical methods; Tafel extrapolation, polarization curves in the absence of either KBH4 or NiCl2, and polarization resistance. In the absence of KBH4 or NiCl2, both the anodic and cathodic polarization curves obeyed the Tafel relation. In the net electroless plating baths however, the anodic polarization curves exhibited a steep current rise followed by a limiting current, while the cathodic polarization remained unchanged. The results indicate that the anodic oxidation of KBH4 is affected by the presence of simultaneous cathodic deposition. Consequently, the estimation from the polarization curves in the absence of NiCl2 gave a higher plating rate than that by weight gain method. On the other hand, the rate estimated from the polarization resistance in the net electroless baths agreed fairly with that of weight gain method under a proper assumption. It is concluded that the rate of the electroless plating of nickel in this bath can be continuously monitored by the polarization resistance method.