| Abstract |
| Alloying element, Nitrogen is known to improve the resistance to pitting corrosing of stainless steels increasing the local pH within the active sites and enhancing repassivation of pits. However chloride ion is believed to promote the localized dissolution, due to the absorption of chloride ions on the passive film. Alloying element Nitrogen and chloride ion may also have influence on the electronic properties of passive films, causing the change of the resistance to the localized corrosion. The electronic properties of passive films formed on austenitic stainless steels, such as 316L and 316LN with different Nitrogen content were investigated in neutral 0.1N Na_2So_4 and 0.N NaCl solutions. In-situ capacitance measurements were performed to obtain the information on the donor concentration and the thickness of space charge region within the passive film. Besides, potentiostatic polarization tests were carried out, to investigate the metastable pitting susceptibility. Results showed that alloying element Nitrogen increased the thickness of space charge layer while chloride ions increased the donor density and the metastable pitting susceptibility. Analyses of AES and AFM indicated that Nitrogen led to the increase in Cr peak within the film and the smoothness on the surface of film. The relationship between semiconducting properties of the passive film and the metastable pitting susceptibility was examined. |
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| Key Words |
| 316L, 316LN, Mott-Schottky plot, AES, Metastable pitting susceptibility |
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