51312-01497-An AC Impedance and XPS Study of the Surface Films on Austenitic Superferritic and Duplex Stainles

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Product Number: 51312-01497-SG

ISBN: 01497 2012 CP

Author: Kevin R. Chasse

Publication Date: 2012

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Austenitic and duplex stainless steels (SSs) may become susceptible to general corrosion and stress corrosion cracking in hot alkaline sulfide solutions particularly when chlorides are present. This study evaluated the electrochemical behaviour of select SSs in alkaline environments of 100 g l-1 sodium hydroxide 55 g l-1sodium sulphide and 10 g l-1 sodium chloride at 90 0C and 170 0C to determine the effect of solution composition and temperature on the corrosion behaviour. Polarization resistance electrochemical impedance spectroscopy and potentiodynamic polarization were carried out on pure Fe Cr Ni and Mo as well as select grades of austenitic SSs (UNS S31603 and UNS S30403) superferritic SSs (UNS S44660 and UNS 44646) and duplex SSs (UNS S32205 UNS S32304 and UNS S32101). Film compositions of select grades of SSs (UNS S31603 UNS S44660 UNS S32205 and UNS S32101) were evaluated with X-ray photoelectron spectroscopy and energy dispersive spectroscopy following exposure at the corrosion potential. Film morphologies were examined with optical and scanning electron microscopes. The film formed on SSs in alkaline sulfide solutions became defective due to the formation of metal sulfides in the oxide film. The films were more defective in the presence of chlorides owing to more dissolution of Fe and Cr.