【摘要】 研究了采用碱式碳酸镍作为镍源在AZ91镁合金表面直接化学镀镍的工艺。该工艺采用酸洗活化一步法,即经过脱脂除油,再用H3PO4、NH4HF2以及缓蚀剂处理,无需活化。通过比较3种酸洗液的应用效果,确定60 mL/L H3PO4,40 g/L NH4HF2,30 g/L H3BO3的混合液作为酸洗液。酸洗最佳pH约为2,时间为25 s。实验发现,该法较HF活化得到的镀层表面颗粒更均匀。该N i-P镀层结合力合格,硬度可达356.7HV。讨论了热处理温度对镀层硬度的影响,结果表明随热处理温度的提高,镀层硬度也随之提高,在热处理温度为250℃时,硬度达最大。通过Tafel曲线分析得出,AZ91镁合金采用该工艺进行化学镀镍后,耐蚀性有了很大改善。更多还原

【Abstract】 Using basic nickel carbonate as the source of nickel,the process of electroless nickel plating on magnesium alloys AZ91 was studied.In the technics,acid picking and activation were completed at one step,that is to say,after degreasing and treatment with the solution containing phosphoric acid,ammonium hydrogen fluoride and corrosion inhibitor,the alloy to be electroless nickel plated needs not to be activated.By comparing the results of three pickling solution,the optimal formulation was determined:（60 mL/L） H₃PO₄,40 g/L NH₄HF₂,30 g/L H₃BO₃.The optimal pH is about 2,time is 25 s.The test results prove that the grains obtained on deposit surface by the method is more even than that by HF activation.The Ni-P deposit has good adhesion,and its hardness reaches 356.7 HV.The influence of heat treatment temperature on deposit hardness was discussed.Results prove that the deposit hardness increases with increasing heat treatment temperature and the highest hardness value is obtained at a temperature of 250 ℃.The analysis of Tafel curve shows that the corrosion resistance of magnesium alloys AZ91 is improved apparently after being electroless nickel plated by above process.更多还原