装饰用铜合金镧-铈复合化学转化工艺及膜层耐蚀性

Preparation and corrosion resistance of La–Ce composite chemical conversion coating for decorative copper alloys

对装饰用H62铜合金进行稀土镧-铈复合化学转化。对转化液组成和工艺条件进行正交优化,得到最优参数为:硝酸镧4 g/L,硝酸铈4 g/L,苯并三氮唑15 g/L,钼酸钠2 g/L,柠檬酸13 g/L,磺基水杨酸9 g/L,十二烷基苯磺酸钠0.4 g/L,温度53°C,时间4 min。该条件下所得La–Ce复合转化膜的厚度为6.2μm,耐硝酸点滴时间为23.16 s。中性盐雾试验、静态浸泡腐蚀试验和电化学阻抗谱测试结果均表明,单一镧盐或铈盐转化膜的耐蚀性优于无稀土转化膜,La–Ce复合转化膜的耐蚀性则最优。

Chemical conversion of decorative H62 copper alloy was conducted using rare earth(La and Ce)salts.The bath composition and process conditions were optimized through orthogonal test as follows:lanthanum nitrate 4 g/L,cerium nitrate 4 g/L,benzotriazole 15 g/L,sodium molybdate 2 g/L,citric acid 13 g/L,sulfosalicylic acid 9 g/L,sodium dodecylbenzenesulfonate 0.4 g/L,temperature 530 C,and time 4 min.The La-Ce composite conversion coating obtained under the given conditions was 6.2μm-thick and endurable to nitric acid dropping corrosion for 23.16 s.All of the results of neutral salt spray test,static immersion corrosion test,and electrochemical impedance spectroscopy measurement showed that the conversion coating prepared with single lanthanum salt or cerium salt was better than that prepared without any rare earth salt,while the La-Ce composite conversion coating had the best corrosion resistance.