| In order to solve the problems of unstable plating solution of electroless nickel-chromium-phosphorus ternary alloy plating and the difficulty of co-deposition of Cr and Ni,a study on the preparation of nickel-chromium-phosphorus ternary alloy coating by electroless plating was carried out.Through single factor and orthogonal experiments,the effects of plating solution composition and process parameters on the deposition process of the coating were investigated in alkaline and acidic systems,respectively,and the results of orthogonal experiments were analyzed.Using modern analysis methods such as scanning electron microscope?SEM?,energy spectrometer?EDS?,X-ray diffractometer?XRD?,electrochemical workstation,etc.,the surface morphology,composition and structure of typical nickel-chromium-phosphorus ternary alloy coating,the content of the metal chromium in the coating,and the corrosion resistance of the coating were characterized.The effects of the concentration of chromium chloride,lactic acid,glycine and potassium oxalate in the plating solution on the deposition rate of the nickel-chromium-phosphorus ternary alloy coating,the content of chromium in the coating and the electrochemical corrosion behavior of the coating in the corrosive medium were studied.According to the orthogonal test results,in the alkaline electroless nickel-chromium-phosphorus ternary alloy plating solution system,when nickel sulfate is 20g·L-1,chromium chloride is 100 g·L-1,sodium hypophosphite is 20 g·L-1,sodium citrate is 90g·L-1,glycine is 15 g·L-1,lactic acid is 40 m L·L-1,boric acid is 40 g·L-1,anhydrous sodium acetate is 18 g·L-1,the bath temperature is 70?,and the bath pH is 8.5,the plating solution of the nickel-chromium-phosphorus ternary alloy electroless plating is stable and the deposition rate is about 10?m·h-1;In the acidic nickel-chromium-phosphorus ternary alloy plating solution system,when nickel sulfate is 50 g·L-1,chromium chloride is 10 g·L-1,sodium hypophosphite is35 g·L-1,and sodium citrate is 10 g·L-1,glycine is 15 g·L-1,lactic acid is 40 mL·L-1,boric acid is40 g·L-1,anhydrous sodium acetate is 18 g·L-1,the bath temperature is 85?,and the bath pH is4.6,the plating solution of the nickel-chromium-phosphorus ternary alloy electroless plating is stable and the deposition rate is about 15?m·h-1.The results show that the concentration of chromium chloride increases and the deposition rate increases.With the increase of the concentration of lactic acid,glycine and potassium oxalate,the deposition rate decreases continuously.The surface morphology of the electroless nickel-chromium-phosphorus ternary coating is a cell structure,and the coating is amorphous and microcrystalline.The self-corrosion potential of the electroless nickel-chromium-phosphorus ternary coating is much higher than that of the nickel-phosphorus binary alloy coating,which moves forward about 0.25V;its charge transfer resistance increases,and the corrosion current density decreases by about two orders of magnitude.The corrosion resistance of the nickel-chromium-phosphorus ternary coating is significantly better than that of the nickel-phosphorus binary alloy coating. |
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