Abstract
The current research of corrosion resistance of stainless steels mainly focuses on characterization of the passive films by point defect mode and mixed-conduction model. The corrosion resistance of the passive films formed on as-received and sensitized AISI304 stainless steel in borate buffer solution were evaluated in this paper. The degree of sensitization and corrosion resistance of AISI304 stainless steels was evaluated by double loop electrochemical potentiodynamic reactivation and electrochemical impedance spectroscopy. The passive films formed on the stainless steels were studied by XPS technique. It was found that as-received specimen had higher pitting corrosion potential and corrosion resistance than sensitized one. The Mott-Schottky results showed that sensitized stainless steel had more defects in the passive film than as-received one. The compositions of the passive films were mainly Cr and Fe oxides according to XPS results.
Highlights
Austenitic stainless steels are widely used in components designed for high temperature applications like nuclear power stations, superheaters, and thermal power plant [1]
The degree of sensitization (DOS) values of both specimens was measured by double loop electrochemical potentiodynamic reactivation (DL-EPR) technique in 0.5 M H 2SO4 + 0.01 M KSCN solution, and microstructure was observed by Scanning Electron Microscope (SEM)
It can be seen that as-received specimen shows almost no ditches in grain boundaries, whereas a considerable number of ditches occur on sensitized specimens
Summary
Austenitic stainless steels are widely used in components designed for high temperature applications like nuclear power stations, superheaters, and thermal power plant [1]. Some localized corrosion such as pitting corrosion [2, 3], intergranular corrosion [4], stress corrosion crack (SCC) [5, 6] were often observed especially in the temperature range of 450‒900 °C. The depletion zone in which chromium concentration is less than 12 wt.% making the material vulnerable to corrosion [7]. The corrosion resistance of stainless steels is basically controlled by the protection of the surface oxide layer. The destruction of the passive films on stainless steels will induce SCC [8,9,10]. Further understanding the compositions and physical characteristics of the passive films
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