CORROSION BEHAVIOR OF PURE Mg BASED ON GENERATION/COLLECTION AND FEEDBACK MODES OF SCANNING ELECTROCHEMICAL MICROSCOPY

Since electrochemical impedance spectroscopy, polarization curve and hydrogen collection were the main technologies for corrosion research of Mg and its alloy. However, those methods only provide the mean information of entire surface of corrosion electrode. In this work, H-2 evolution and active sites of pure Mg from localized sites (point, line and surface) in NaCl and Na2SO4 solution based on generation/collection and feedback modes of scanning electrochemical microscopy (SECM) were studied. The results indicate that both cathodic and anodic polarization are in favor of H-2 evolution in NaCl and Na2SO4 solution, which is well in line with the negative difference effect by the classical H-2 collection, but the SECM results show that the H-2 evolution in localized sites is not uniform and stable. The H-2 evolution rate increases with NaCl concentration increasing, which is opposite in Na2SO4 solution. The higher NaCl concentration, anodic polarization and lower pH value accelerate the formation of active sites on pure Mg surface.