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采用化学浸泡法在黄铜表面制得镧转化膜,转化液组成与工艺条件为:硝酸镧3.5～5.5g/L,苯并三氮唑8.0～12.0g/L,磺基水杨酸8.0～12.0g/L,柠檬酸15.0g/L,温度60℃,pH4,时间3min。采用原子吸收光谱和电化学法研究了黄铜/镧转化膜在模拟雨水中的腐蚀行为。在相同的浸泡时间内,黄铜/镧转化膜在模拟雨水中溶解的铜离子质量浓度低于黄铜基体。在酸性范围内,模拟雨水的pH越高,黄铜/镧转化膜越不容易被腐蚀。镧转化膜对溶解于雨水中的SO2-4和Cl-较敏感,Cl-含量的增加使黄铜/镧转化膜的点蚀增强,SO2-4含量的增加使膜层整体发生严重腐蚀;NO-3含量则对其腐蚀行为的影响不大。黄铜/镧转化膜在pH=3.29的模拟雨水中的腐蚀经历3个阶段。
The lanthanum conversion coating was prepared by chemical immersion on the brass surface. The composition and technological conditions of the conversion liquid were as follows: lanthanum nitrate 3.5-5.5 g / L, benzotriazole 8.0-12.0 g / L, sulfosalicylic acid 8.0-8.0 mg / 12.0g / L, citric acid 15.0g / L, temperature 60 ℃, pH4, time 3min. The corrosion behavior of brass / lanthanum conversion coatings in simulated rainwater was studied by atomic absorption spectroscopy and electrochemical methods. In the same immersion time, the copper / lanthanum conversion coating dissolved in simulated rainwater had a lower mass concentration of copper ions than the brass substrate. In the acidic range, the higher the pH of the simulated rainwater, the less susceptible the brass / lanthanum conversion coating is to corrosion. Lanthanum conversion coating was more sensitive to SO2-4 and Cl- dissolved in rainwater. The increase of Cl- content enhanced the pitting corrosion of brass / lanthanum conversion coating and the increase of SO2-4 caused serious corrosion of the coating. -3 content has little effect on its corrosion behavior. The corrosion of the brass / lanthanum conversion coating in simulated rainwater at pH = 3.29 goes through three stages.