Preparation And Corrosion Resistance Of Ni-Cr-P Alloy Coating

The Ni-Cr-P alloy coating prepared by the electrodeposition method has good corrosion resistance and high hardness,and is easy to operate,which is of great significance for its research.At present,most of the Ni-Cr-P alloy coatings are obtained by electroless plating,and the method of preparing Ni-Cr-P alloy coating by electrodeposition has rarely been studied.Therefore,this paper uses the electrodeposition method to explore the corrosion resistance of Ni-Cr-P alloy coating and compare it with the corrosion resistance of Ni-P alloy coating.In this paper,by studying the effects of changes in main salt concentration,current density and temperature on the properties and structure of the coating,the best formulation and process parameters are screened.The Formula is:NiSO₄ 5 g/L,NaH₂PO₂·H₂O 0.1 g/L,CrCl₃·6H₂O 100 g/L,H₃BO₃ 30 g/L,C₆H₅NaO₇·2H₂O 90 g/L,NH₄Cl 80 g/L,KCl 16 g/L,C₁₂H₂₅NaO₄S 0.5 g/L,KF 1 g/L,C₇H₅NO₃S 1 g/L.Process parameters:T 50^°C,cathode current density 150 mA/cm²,pH 3.5.The surface morphology and hardness of the coating were analyzed.The results show that the surface of the coating has uniform and fine crystals without cracks and high hardness.In order to compare the corrosion resistance of Ni-Cr-P and Ni-P alloy coatings,the polarization curves,immersion corrosion experiments and electrochemical impedance spectroscopy of the coatings after corrosion were studied.The results show:The corrosion resistance of amorphous Ni-Cr-P alloy coating in 3.5%NaCl solution increases with the increase of Cr content,and the corrosion resistance is better than that of Ni-P alloy coating.In the 1 mol/L hydrochloric acid solution,when the P content is similar,the corrosion resistance of the crystalline Ni-Cr-P alloy coating is worse than that of the Ni-P alloy coating,but as the corrosion time increases,corrosion resistance will be better than Ni-P alloy coating;For the case where the P content differs a lot,the corrosion resistance of the crystalline Ni-Cr-P alloy plating layer is inferior to that of the Ni-P alloy plating layer.