Effects of NH4F on the deposition rate and buffering capability of electroless Ni-P plating solution

The deposition rate and buffering capability of alkaline electroless Ni-P plating solution containing ammonium fluoride (NH4F) have been investigated. When the NH4F concentration is below 10g L-1, the deposition rate is improved with the addition of NH4F, reaching the maximum value at 2g L-1. The buffering capability of solutions is found to be improved with increasing NH4F concentration. Due to the improvement of buffering capability, refined and compact Ni-P coatings with homogeneous elemental distribution of P have been achieved. Therefore, both the corrosion resistance and microhardness of Ni-P coatings are significantly improved. The mechanism of NH4F improving the deposition rate and the buffering capability is discussed.