Investigation of depassivation-repassivation behavior of metal surfaces using micro-indentation test

A micro-indentation test was developed to investigate mechano- electochemical properties of metal surfaces. In solution environment, the contact of an indenter with an iron passive surface causes depassivation of the surface when the surface deforms plastically. The scale of the depassivation is dependent on hardness and deformation area of the substrate iron. Repassivation following depassivation is affected by not only electrode potential of the specimen and solution conditions (pH and electric conductivity of the solution) but also dislocation in the substrate iron. Furthermore, the micro-indentation test is useful as a rupture technique of the passive film in order to examine the corrosion resistance of stainless steels. It enables to control the deformation area of metal surfaces at an intentional site in a micrometer-order and to serve an in-situ measurement of electrochemical responses. This technique is suitable for consideration of the mechanism and kinetics of depassivation-repassivation behavior of the surface depending on fine metal structures.