70Cu—30Ni合金海水腐蚀产物膜形成过程

PROCESS OF FORMATION OF CORROSION FILMS ON ALLOY 70Cu-30Ni IN SEAWATER

本文研究了70Cu－30Ni合金海水暴露不同时间腐蚀产物膜特征和成分变化。研究表明，该合金腐蚀产物膜内存在一个富Ni区，富Ni区随着暴露时间延长变宽且Ni的富集程度增加，富Ni腐蚀产物膜充当阳极，从而保护基体。长期暴露所形成的腐蚀产物膜出现裂纹或沟，这是由于膜下基体在这些位置存在结构或成分的变化使膜的生长速度减慢或者内应力导致膜的破裂。随着外层膜的溶解与脱落，原裂纹或沟成为凸出条纹，凸出条纹中Ni与Cu的浓度比高于条纹之间区域中Ni与Cu的平均浓度比，凸出条纹优先溶解使膜表面趋向平整。膜中碳量随暴露时间延长而增加，因此可以认为碳来源于海水而不是来自加工残碳膜。

The characteristics and composition changes of the corrosion films of alloy 70Cu-30Ni immersed in seawater for different times were investigated.The results show that there is a Ni-rich zone in the films, which becomes wider and higher in the degree of Ni enrichment with increasing the immersed time. The film rich in Ni serves as an anode so as to protect the matrix. For the change of the structure or composition or for inner stress making the film broken, cracks or trenches appear in the film immersed in seawater for long time.With the solution and scaling off of the outer layer,the cracks or trenches become convex lines. Because the concentration ratio Ni / Cu at the convex lines is higher than average ratio Ni/Cu in the zone between convex lines,the preferred dissolution of convex lines leads the surface of the film to smoothness.The carbon in the film increases with increasing immersion time and can be thought to be from seawater not from residual carbon films.