挤压变形对金属镁化学镀镍的影响

Effect of Extrusion Deformation on Electroless Nickel Plating of Magnesium

用硫酸盐镀镍溶液对挤压变形前后的金属镁进行化学镀镍,并用动电位法研究了镀层在3.5%NaCl溶液中的耐蚀性能。结果表明:由于挤压变形前金属镁组织不均匀,镀层的胞状组织也不均匀,胞与胞交界处存在一定缺陷,造成镀层耐蚀性能较差;挤压变形后金属镁的化学镀镍反应进行较快,镀层颗粒细小均匀,为镀层有良好的耐蚀性能提供了结构条件。挤压变形后化学镀镍层对镁基体有一定的保护作用。

A nickel sulfate bath was used to prepare electroless nickel coatings on magnesium before and after extrusion deformation.The effect of extrusion on the corrosion resistance of the electroless Ni-P coatings was investigated.Thus the corrosion resistance of the electroless Ni-P coatings in 3.5% NaCl solution was evaluated using potentiodynamic polarization method.It was found that magnesium before extrusion had non-uniform microstructure,so did the corresponding electroless Ni-P coating,therefore the coating had poor corrosion resistance because of the existence of the inter-cell defects at the boundaries.Contrary to the above,the reaction on the extrusion-deformed Mg in the electroless Ni plating process was fast,and the resulting Ni-P coating had fine grains and uniform microstructure,which contributed to increasing the corrosion resistance.Moreover,electroless Ni plating on the extrusion-deformed Mg was more effective in preventing the Mg substrate from corrosion.