Abstract
This study aims at assessing the degree of susceptibility to intergranular corrosion of the UNS S31803 duplex stainless steel and the 0.4% Mo austenitic stainless steel through the double-loop electrochemical potentiodynamic reactivation (DL-EPR) test. Both steels were subjected to isothermal treatments at 650ºC and 900ºC in order to compare the effect of temperature on the respective degrees of sensitization. It was observed that the 0.4% Mo austenitic stainless steel presented a higher degree of sensitization and, consequently, a greater susceptibility to the intergranular corrosion process when compared to the UNS S31803 duplex stainless steel in the two temperatures studied. It was also observed that, for both steels, the heat treatment at 900ºC resulted in a higher degree of sensitization when compared to the heat treatment at 650ºC.
Highlights
Duplex stainless steels (DSS) are widely used in manufacturing critical components in different industrial fields, such as petrochemical, food, oil and nuclear industries
double-loop electrochemical potentiodynamic reactivation (DL-electrochemical potentiodynamic reactivation (EPR)) tests were performed on 3 specimens of each of the steels studied in each heat treatment condition
The DL-EPR tests started at the steel corrosion potential and were carried out with a scan rate of 1.67 mV(SCE)/s, as previously reported
Summary
Duplex stainless steels (DSS) are widely used in manufacturing critical components in different industrial fields, such as petrochemical, food, oil and nuclear industries. The precipitation of carbides and phases may promote the sensitization of stainless steels, making them susceptible to intergranular corrosion[3]. The 0.4% Mo austenitic stainless steel, studied in this paper, has lower chromium content (17%) compared to AISI 304 austenitic stainless steel (18-20%) Both steels have approximately the same pitting corrosion resistance due to the presence of Mo in the first steel. The two studied steels can be competitive in many applications considering their distinct properties due to microstructural differences In this case, in relation to resistance to pitting corrosion, this work presents important information on the behavior of the two steels when subjected to aging temperatures of 650oC and 900oC. The higher the value of the reactivation current (ir), the lower the stability of the protective film and, the greater the susceptibility to localized corrosion
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