Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
This report describes a new route for direct electroless Ni-P plating on magnesium alloys using nickel sulfate as the main salt component. The surface morphology, chemical composition and corrosion resistance of coatings were determined using SEM, EDX and electrochemical polarization techniques. | VNU Journal of Science: Natural Sciences and Technology, Vol. 33, No. 2 (2017) 58-66 A New Route for Direct Electroless Ni-P Plating on Magnesium Alloys Tran Tan Nhat1,*, Bui Xuan Vuong2 1 2 HCM City University of Food Industry Sai Gon University, 273 An Dương Vương, 5 District, Ho Chi Minh City Received 03 November 2016 Revised 24 March 2017; Accepted 28 June 2017 Abstract: This report describes a new route for direct electroless Ni-P plating on magnesium alloys using nickel sulfate as the main salt component. The surface morphology, chemical composition and corrosion resistance of coatings were determined using SEM, EDX and electrochemical polarization techniques. Ni-P coatings with good corrosion resistance and high adhesion were obtained using this route and improved pretreatments. A mixture of H3PO4 and HNO3 was used as a pickling solution for Mg substrate pretreatment. A coarse surface was produced via the developed pickling procedure. A mechanical occlusive force is believed to exist between the coatings and the substrates. Twice activations, K4P2O7 and NH4HF2 as activation components, respectively, were applied for the pretreatment of magnesium alloy plating. An optimal F/O ratio on the Mg substrate surface was obtained by this pretreatment method. The activation film has insoluble partial fluorides which can depress the active points on substrate surface against the reaction of Mg with Ni2+ and H+ in the plating bath. A highly stable bath with pH 5 buffer was identified. The advantages of the developed process include chromium-free, low fluoride, and high bath stability. It is applicable for the production of motorcycle part plating. Keywords: Ni-P, electroless plating, Mg, surface, alloy. 1. Introduction reactivity and poor corrosion resistance of magnesium alloys. This is one of the major reasons why the widespread applications of magnesium alloys have been greatly limited [57]. Hence, it is of great importance to increase the corrosion resistance
