Effects of pH Value and Concentration of Solution on P Content and Deposition Rate during Electroless Ni-P Plating on Aluminum Substrate Surface

The effects of the factors including pH value,concentration of main salt,reductant and complexing agent of the solution on the deposition rate and P content of the electroless Ni-P plating on aluminum substrate surface were investigated by the orthogonal test.The results show that the effect of the solution pH value was the most significant,and it was followed by main salt concentration and reductant concentration.In the selected acid solution,with the increase of pH value in the range of 3.5 to 6.0,the P content in the solution decreased from 225at%(pH=3.5) to 12.6at% (pH=6.0).And the deposition rate increased till the rate reached the maximum value of 21.0 μm·h-1 (pH=5.0),and then it had little change.The P content decreased with the increase of main salt concentration of NiSO4,but increased with the increase of reductant concentration of NaH2PO2.The deposition rate increased with the increase of the concentration of main salt and reductant.An excellent Ni-P plating with 152at% P and deposition rate of 21.0 μm·h-1 could be obtained.