| Summary: | 碩士 === 國立成功大學 === 材料科學(工程)學系 === 85 === Abstract In this study, the effect of
polythionic acid on the electrochemical behaviors of four
different stainless steels (SSs)，namely 430 SS, 444 SS, 316 SS,
and 2205 duplex SS in 20wt% NaCl solution were investigated. The
effects of concentration in S4O6= solution were also
investigated. Potentiodynamic polarization curves
measurement was used to investegated the effect of polythionic
acid on electrochemical characteristics of stainless steels in
20wt% NaCl solution. For 430 SS the passive regions were neither
observed inpolythionic acid nor in 20wt% NaCl with polythionic
acid solution. Potentiodynamic polarization curves reveal that
the addition of polythionic acid in 20wt% NaCl solution reduce
the transpassivation potential and passive region, that is,
polythionic acid increase the pitting suscepitibility for the
444 SS and 316 SS. The Polytionic acid has no effects on
pitting potential of 2205 DSS in 20wt% NaCl solution. The
pitting potentials from high to low were 2205 DSS, 444 SS, 316
SS and 430 SS in 20wt% NaCl solution and in 20wt% NaCl added
polythionic acid solution. Pitting corrosion were observed not
only in 20wt% NaCl for 430 SS, 444 SS, 316 SS and 2205 DSS in
20wt% NaCl solution but also addition polythionic acid to 20wt%
NaCl solution. The black corrosion products were found on the
surface of the 430 SS, 444 SS, 316 SS and 2205 DSS, in solutions
containing polytionic during OCP test. The results of XPS
analysis were shown that the corroion products of 430 SS and 444
SS were FeS; the corrosion products of 316 SS and 2205 DSS were
FeS and NiS. The open circuit potential from high to low were
316 SS, 2205 DSS, 444 SS, 430 SS in all the above environments.
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