新型氯化钾镀锌三价铬钝化剂和膜层耐蚀性

Novel trivalent chromium passivators for zinc coatings obtained from potassium chloride electrolytes and the corrosion resistance of passivation films

通过测定Tafel极化曲线、交流阻抗谱和进行盐雾试验,研究了新型三价铬彩色钝化剂SF-571和蓝白钝化剂SF-572对镀锌层耐蚀性能的影响,并与进口钝化剂进行对比。氯化钾镀锌工艺为:KCl200g/L,ZnCl250g/L,H3BO335g/L,柔软剂30mL/L,光亮剂1.5mL/L,25°C,25min,电流密度2A/dm2。电化学分析表明,所有镀锌层钝化膜在1%NaCl溶液中均存在钝化现象,采用自制钝化剂SF-571和SF-572所得膜层的耐腐蚀性能达到或优于用进口钝化剂所得膜层。对比膜层的表面形貌可知,自制钝化剂钝化所得膜层表面更平整、致密。

The effects of novel trivalent chromium passivators SF-571 （iridescent） and SF-572 （blue-white） on corrosion resistance of zinc coating were studied by Tafel polarization method, electrochemical impedance spectroscopy, and salt spray test, and compared with the imported ones. The zinc coatings were obtained in a potassium chloride bath comprising KC1200 g/L, ZnC12 50 g/L, H3BO3 35 g/L, softener 30 mL/L, and brightener 1.5 mL/L at 25 ℃ and 2 A/dm2 for 25 rain. The electrochemical analysis shows that all of the passivation films has a passivation hehavior in 1% NaCl solution. The corrosion resistance of the films obtained with SF-571 and SF-572 passivators is equivalent or superior to that obtained with the imported passivators. The comparison of surface morphology indicates that the surfaces of the films obtained with homemade passivators are smoother and denser.