紫铜海水管焊接部位在人工海水中的腐蚀行为

通过阳极极化曲线、交流阻抗测试、扫描电镜研究了紫铜海水管焊接部位在人工海水中的腐蚀行为.结果表明：紫铜、白铜焊缝和黄铜焊缝在人工海水中的阳极过程类似，相同电位下，白铜焊缝的电流密度最小，耐蚀性最佳，与阻抗测试结果一致.黄铜焊缝在电位-0.012 V时出现电流峰，腐蚀产物膜多孔、疏松，随后电极进入钝化区，钝化膜由Cu₂O、CuCl和ZnO组成;随电位升高，钝化膜溶解，发生铜锌置换反应，沉积的Cu导致活性电对的形成，增加了合金的腐蚀速度;当电位为＋0.87 V时，电极表面富集了针状锡和锡的氧化物.随后，电极表面积累的锡和锡的氧化物及腐蚀产物层对脱锌腐蚀有一定的阻碍作用，电流密度有所下降，最后腐蚀达到一种动态平衡，腐蚀机制为溶解-再沉积机理.

Corrosion behavior of welded joints of copper pipe in artificial seawater

The corrosion behavior of the welded joints of copper pipe in artificial seawater was studied with anodic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM).Experiment results indicated that the anodic processes of copper, cupronickel-welded joint and brass-welded joint were similar in artificial seawater.At the same electrode potential, the corrosion current of cupronickel was the lowest and the corrosion resistance was the best,which is consistent with the EIS result.The current density peak of brass welded line appeared at -0.012 V, and a porous corrosion film was formed.The electrode was passivated subsequently.The passivation film was made up of Cu_2O,CuCl and ZnO.The passivation film dissolved with electrode potential, and displacement deposition took place between Cu and Zn.The copper redeposition on the electrode surface induced the increase of electrode activity and corrosion rate.At an electrode potential of 0.87 V, the electrode surface was rich of acicular Sn and stannum oxide.This film would prevent the electrode from dezincification, and the current density decreased and homeostasis was reached at the same time.The corrosion mechanism of brass welded line in artificial seawater was dissolution/redeposition.