添加剂对AZ91D镁合金化学镀镍磷耐蚀性的影响研究

Effect of Annexing Agent on Corrosion Resistance of Electroless Ni-P Alloys of AZ91D Magnesium Alloy

采用常温碱性超声波清洗、酸洗和活化的前处理工艺在AZ91D镁合金表面化学镀镍,研究了辅助络合剂氨基乙酸和加速剂巯基乙酸对镀层耐蚀性的影响。结果表明:镀层表面由Ni-P固溶体组成,呈现尖锐的晶态峰,磷原子与镍原子形成置换固溶体,表面平整致密,无明显缺陷。氨基乙酸含量对镀层耐蚀性和腐蚀速率影响不大,随着巯基乙酸含量的增加,镀层腐蚀电位先升高后降低,腐蚀速率整体比镁合金基体慢,镀层总体呈现钝化趋势,在4 g/L时腐蚀电位最高。

Alkaline ultrasonic cleaning at room temperature, acid pickling and activation process have adopted as the pretreatment of AZ91D magnesium alloy for nickel electroless plating. The effect of auxiliary complexing agent glycine and accelerator thioglycollic acid on the corrosion resistance of the coating on AZ91D magnesium alloy has been researched. The result showed that the coating consisted of Ni-P solid solution and presented as sharp crystalline peak. Phosphorus atoms and nickel atoms formed substitutional solid solution. The surface was smooth, dense and had no significant defect. The content of glycine had not remarkable effect on the corrosion resistance and corrosion rate of the cladding material. The corrosion potential of the cladding material increased firstly and decreased then with the increase of the content of thioglycolic acid . The entire corrosion rate of Ni-P plating was slower than magnesium alloy substrate. The entirety of Ni-P plating showed a trend of passivation. It had the highest corrosion potential with thioglycolic acid 4 g/L.