Characterization of a Stressed Passive Film Using Scanning Electrochemical Microscope and Point Defect Model

Abstract

The corrosion resistance of passive film is investigated by in situ scanning electrochemical microscopy (SECM), and is also diagnosed by modified point defect model (PDM). Thus the constant rate related to defect reactions present in the passive film, can be obtained. SECM results indicate that both compressed and tensile stress decreases the stability of passive film, leading to an increase in surface reactivity and dissolution rate—which is possibly due to the decreased binding force between atoms caused by the stress and therefore make them more easy to dissolve. PDM results indicate that the reason of the decreased stability is an increase in the rate constant of defect reactions present in the passive layer, including transportation rate of oxygen and cation dissolution rate.