Study Of Preparation And Application Of Duplex Ni-P Alloy Layer And Ni-P/PTFE Composite Layer

The history and current situation of electroless nickel were stated in this paper, and concentrations'variation of tartaric, citric, lactic, malic, glutamic, glycine's effects on the deposit rate of electroless nickel were investigated through experiment.On the basis of previous studies, according to the theory on electroless nickel and orthogonal, formulations of citric-glutamic, tartaric-glutamic, malic-glutamic and tartaric-glutamic-propionic were designed and optimized by taking the deposit rate, the corrosion potential as the main index, and taking porosity, phosphorus content as subsidiary index. Three formulations with overall performance were received.Their components, process parameters and performance were listed as following: Formulation A:NiSO4·6H2O:40 g/L, NaH2PO2:27 g/L, tartaric:15 g/L, sodium glutamate: 31 g/L, temperature T=86℃, pH= 6.5, plating rate v= 10/μm/h, Ecorr=-550 mV, porosity:2/cm2, phosphorus content of about:3wt%; Formulation B:NiSO4·6H2O:40 g/L, NaH2PO2:25g/L, citric:18g/L, sodium glutamate:20g/L, temperature T=86℃, pH =5.5, plating rate v= 7μm/h,Ecorr=-430mV, porosity:3/cm2, phosphorus content of about:9 wt%; Formulation C:NiSO4·6H2O:20 g/L, NaH2PO2:40 g/L, tartaric:20 g/L, sodium glutamate:28 g/L, temperature T= 84℃, pH= 5.8, plating rate v= 8μm/h, Ecorr =-293mV, porosity:2/cm2, phosphorus content of about:11 wt%.The corrosion resistance of duplex-layer was estimated by corrosion paste method. The results indicated that duplex layer, whose composition was Ni-P (Ecorr was-550mV, thickness:8μm, outer sublayer)/Ni-P (Ecorr was-295 mV, thickness:16μm, inner sublayer), had the highest corrosion resistance. In the third cycles of corrosion testing, the level of corrosion of substrate was still in eight and the the level of corrosion of coating in four or more.On the basis of Gugliemi's two-steps absorption codeposition mechanism and Ming-Der Ger's codeposition model, a two steps'adsorption mode modified by competitive adsorption theory was proposed.The effects of the concentration of the PTFE emulsion and the FC-4 surfactant were studied. The contact angles of Ni-P/PTFE layers to deionized water were measured by a DatapHysics OCA-20 contact angle analyzer. The results indicated that when the PTFE emulsion concentration was 12.96 ml/L, FC-4 surfactant is 1.5ml/L, the contact angle of the coating to deionized water was maximum about 128°. The results indicated that, under the specific precondition, the mode fitted the results very well.