Study on the correlation between passive film and AC corrosion behavior of 2507 super duplex stainless steel in simulated marine environment

摘要

The correlation between passive film and AC corrosion behavior of 2507 super duplex stainless steel (SDSS) has been investigated in NaCl solution under various AC current densities using the polarization curve, EIS test, Mott-Schottky curve and with immersion test. Additionally, the corrosion mechanism of passive film under AC interference was studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). The test results indicate that the roughness of the passive film increases and the composition as well as electronic properties change under AC interference. Moreover, AC interference can enhance the dissolution of passive film, resulting in a non-uniform destructive effect to the film. The passivity of stainless steel degrades and pitting sensitivity increases as the increase of i(AC). When i(AC) is less than 100A/m(2), the pit initiation sites mainly concentrate on the austenite phase and the boundary between ferrite and austenite phase. However, a great number of pits occur on the ferrite phase while iAC equals to 200A/m(2).