紫铜表面新型无铬转化膜的耐蚀性能

Corrosion Resistance of Novel Chrome-Free Conversion Film on Red Copper

目前,常规紫铜无铬转化液主要由苯骈三氮唑(BTA)、配位剂和表面活性剂组成,所得转化膜的耐蚀性较差。在常规无铬转化液中加入钼酸钠和硝酸镧,并确定了一种环保型紫铜表面无铬成膜工艺:12 g/LBTA,8 g/L Na2MoO4,4 g/L La(NO3)3.6H2O,10 g/L C6H8O7,4 g/L C7H6O6S.2H2O,温度50℃,时间5 min。通过中性盐雾试验测试了所得转化膜的耐蚀性;采用极化曲线和交流阻抗谱分析了转化膜在1 mol/L HCl中的电化学行为,同时用场发射扫描电镜(FESEM)观察了转化膜的表面形貌。结果表明:本工艺无铬、环保,可在紫铜表面形成完整、致密的转化膜,缓蚀率达98.8%,耐蚀性优于铬酸盐钝化膜和常规无铬钝化膜。

Sodium molybdate and lanthanum nitrate were added into conventional Cr-free conversion fluid,and the process for fabricating Cr-free passivation film on red copper was established.The corrosion resistance of as-prepared Cr-free conversion film was evaluated using neutral salt-spray test,and its electrochemical behavior in 1 mol/L HCl was examined by measuring the polarization curve and alternating electrochemical impedance spectrum.The morphology of as-prepared conversion film on red copper was observed using a scanning electron microscope.It was found that desired conversion fluid consisted of 12 g/L BTA,8 g/L Na 2 MoO 4,4 g/L La(NO 3) 3.6H 2 O,10 g/L C 6 H 8 O 7 and 4 g/L C 7 H 6 O 6 S.2H 2 O;and proper film-formation temperature and time were 50 ℃ and 5 min.The established process was free of Cr and environmentally acceptable,and could be adopted to prepare complete and compact conversion film with an inhibition efficiency of 98.8% on red copper.Besides,as prepared conversion film possessed better corrosion resistance than chromate conversion film and conventional Cr-free conversion film.