The Phosphorous Incorporation Process In Electroless-Deposition Ni-P Alloy And Its Effect On Properties Of Ni-P Coatings

Physical and chemical properties of electroless plating nickel (EN) coatings can be greatly affected by phosphorus content in electroless Ni-P alloy. In order to control phosphorus content in coatings effectively, phosphorus generation mechanism and influencing factors should be realized fully. However, there are no detail researches to report that process.Thus, electrochemical and quantum chemical methods were applied to deeply study phosphorus generation mechanism and influencing factors in this paper. The measurement results were obtained by X-ray fluorescence spectrometer (XRF), in order to ensure accuracy of phosphorus content data. Furthermore, the electrochemical noise (ENA) measure was applied to monitor electroless plating nickel process. According experimental and measuring results, the phosphorus generation models were established. Moreover, the effect mechanism of electroless plating nickel brightener on nickel deposition and the effect of phosphorus content on corrosion property of electroless plating black nickel were discussed in this paper.The effect of complexing agents on phosphorus content of electroless nickel deposits was investigated by electrochemical measurement and composition analysis of Ni-P deposits by XRF. Phosphorus generation was induced by nickel species, and was greatly affected by the structures of nickel complexing agents, according to the cyclic voltammograms of NiSO4, NaH₂PO₂, NiSO₄ and NaH₂PO₂, and NiSO₄ and NaH₂PO₂ added complexing agents. The plating measuring results were agreed well with the conclusion. Thus, phosphorus generation mechanism of complex heterocatalysis was proposed. Meanwhile, concentration ratio of NiSO₄ and NaH₂PO₂ also greatly affects the phosphorus content. Then direct generation mechanism of phosphorus incorporating with nickel was proposed. The low, middle and high-phosphorus EN baths were obtained based on both mechanisms.Phosphorus generation fully originates from reduction reaction of hypophosphorous during EN process. The reduction reaction was detailed discussed by ab initio method according to molecular orbital theory using...