空化作用下奥氏体不锈钢空泡腐蚀的过程与AFM形貌

AFM Morphology and Cavitation Corrosion Process of Austenitic Stainless Steel by Cavitation

在研究奥氏体不锈钢的空泡腐蚀规律和SEM形貌的基础上,采用原子力显微镜(AFM)观察奥氏体不锈钢空泡腐蚀过程中的形貌变化,并利用电化学极化技术进一步验证.结果表明:AFM腐蚀形貌并非呈塑性断口特征,而是晶界优先腐蚀、晶粒凸显且受到明显磨损与腐蚀的形态.电化学极化研究进一步验证在空化作用下不锈钢表面的钝化膜由局部被冲蚀逐渐转变为全部被冲蚀,且空化作用主要促进电极的阳极溶解过程,而对阴极过程影响不显著.

Atomic force microscopy（AFM） was adopted to investigate the morphology of 304 austenitic stainless steel suffered from cavitation corrosion,and then electrochemical technology was used further to verify the changes of corrosion morphologies on the base of the previous study on the cavitation corrosion behavior and SEM morphology of the same steel.The cavitation corrosion morphology of the austenitic stainless steel was not of typical ductile fracture appearance. Corrosion preferentially started and mainly developed on grain boundaries with very different crystallographic orientations,resulting in protruded grains which were subjected to serious erosion and corrosion.The erosion processes of passivation films on the surface of the austenitic stainless steel from part to the whole were further verified by electrochemical polarization test and it was found that cavitation mainly accelerated anodic dissolution and did not markedly influenced cathodic process during cavitation corrosion of the 304 austenitic stainless steel.