Zn-Ni合金镀层的黑色钝化工艺研究

Black passivation process of Zn-Ni alloy deposits

在含Ni为10%～14%的Zn Ni合金镀层上先钝化再进行封闭处理,可获得色泽均匀、结晶细致的转化膜。讨论了钝化工艺条件及封闭剂、pH值对转化膜耐蚀性的影响。经过正交实验和单因素实验,确定了最佳钝化配方为:40g/L铬酐、40mL/L醋酸、10g/L成膜促进剂、0 45g/L硝酸、温度20℃、时间30～40s。研究了封闭条件,确定的封闭剂的组成为:120～220g/L硅酸钠,1～3g/L氟化钠,0 1～0 3g/L硫酸锂,最佳pH值为10 5。硫酸铜点滴实验、中性盐水浸泡实验、扫描电镜以及交流阻抗测试表明:Zn Ni合金镀层先经钝化再经封闭处理后耐蚀性能明显提高。该钝化工艺操作简单,具有应用价值。

Uniform and dense conversion film can be gained on the surface of Zn-Ni alloy deposits containing 10%～14% of Ni by using passivation sealing technology. The influences of passivation conditions and pH value of sealing (agent) on the corrosion resistance of the conversion film were studied. The optimized passivation formula was determined (by orthogonal) test and single factor test as follows: 40 g/L of Cr_2O_3, 40 mL/L of acetic acid, 10 g/L of accelerator, (0.45 g/L) of nitric acid, temperature of 20 ℃ and time of 30～40 s. Sealing conditions were investigated. The components of sealing agent are as follows: 120～220 g/L of Na_2SiO_3, 1～3 g/L of NaF, 0.1～0.3 g/L of Li_2SO_4, and the optimized pH value is 10.5. CuSO_4 dropping corrosion test, NSS-test, SEM and electrochemical impedance spectroscopy measurements show that the corrosion resistance of Zn-Ni alloy deposit is increasing obviously by passivating firstly and then sealing. The passivating process is easy-to-operate and can be applicable to production.