热浸锌-5％铝合金镀层硅酸盐钝化工艺

摘要

The hot-dip galvanized Zn-5％Al alloy coating was passivated in a silicate solution containing 5wt％ SiO2.The effects of the modulus (i.e.the molar ratio of SiO2 to Na2O) of silicate solution,passivation temperature and time as well as drying temperature on corrosion resistance of passivation film to neutral salt spray were studied.The optimal process conditions of silicate passivation were determined as follows:modulus of silicate solution 4.0,passivation temperature 80 ℃,passivation time 60 s,and drying temperature 125 ℃.The surface morphology and corrosion resistance of the film obtained under the optimized process conditions were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS).The silicate passivation film obtained under the optimal conditions is uniform,complete and transparent,and efficiently improves the corrosion resistance of hot-dip galvanized Zn-5％Al alloy coating.%采用含5％(质量分数)SiO2的硅酸盐溶液对热浸Zn-5％Al合金镀层进行钝化,研究了溶液模数(即SiO2与Na2O的摩尔比)、钝化温度、时间以及烘干温度对钝化膜耐中性盐雾腐蚀性能的影响.硅酸盐的最优工艺条件为:模数4.0,钝化温度80℃,钝化时间60 s,烘干温度125℃.采用扫描电镜(SEM)和电化学阻抗谱(EIS)表征了最优工艺条件下所得膜层的表面形貌和耐蚀性.在最优工艺下所得硅酸盐转化膜均匀、完整、透明,能有效改善热浸Zn-5％Al合金镀层的耐蚀性.