镀锌层硅酸盐彩色钝化工艺

Silicate Color Passivation Technology for Zinc Coating

镀锌层无铬彩色钝化已成为重要的研究方向。研究了硅酸盐无铬彩色钝化工艺条件对钝化膜性能的影响,确定了最佳钝化工艺:30.0 g/L Na2SiO3,25.0 g/L H2SO4,25.0 g/L H2O2,0.1 g/L CuSO4,pH值1.5～2.5,钝化时间10～100 s。最佳工艺条件下,分别对酸性和碱性镀锌件进行硅酸盐彩色钝化,并与六价铬盐钝化层的性能进行了对比。结果表明:镀锌层硅酸盐钝化可以在表面获得彩色、光亮、均匀的钝化膜,膜层的颜色是由膜的化学组成和光的干涉共同作用的显现;耐蚀性能与六价铬盐钝化膜相当,耐中性盐雾腐蚀可达到200 h,且用于碱性镀锌的钝化效果明显优于酸性镀锌;该工艺成本低,无污染,有望代替传统铬酸盐彩色钝化工艺。

The effect of technological conditions for chromium-free silicate coloring passivation of Zn coating on the properties of the passivation film was investigated,and the optimal technological condition was established.Then Zn coatings obtained from an acidic bath and an alkaline bath were separately passivated under the optimal conditions,and the properties of as-obtained passivation films were compared with that of hexavalent chromate passivation film.Results indicate that color,bright,and uniform passivation film can be well prepared on Zn coatings by making use of silicate passivation technology.The passivation fluid with the optimal composition consists of 30.0 g/L Na2SiO3,25.0 g/L H2SO4,25.0 g/L H2O2,and 0.1 g/L CuSO4.The optimal pH value of the passivation fluid is suggested as 1.5~2.5,and the optimal passivation time is determined to be 10～100 s.The passivation film obtained under the optimal passivation condition possesses good corrosion resistance which is comparable to that of hexavalent Cr passivation film,showing endurance against salt-spray for up to 200 h.Besides,silicate passivation technology is more suitable to Zn coating prepared from an alkaline bath,and it is cost-effective and has no pollution to environment,showing promising potential as an alternate technology for conventional chromate color passivation process.