Abstract
This work investigates the influence of deleterious phases precipitation on the corrosion resistance of two wrought superduplex stainless steels UNS S32750 with similar composition, but different grain sizes. Isothermal treatments were carried out to introduce different amounts of deleterious phases, such as chi (χ), sigma (σ) and secondary austenite (γ2). The specimens were tested by double loop electrochemical potentiodynamic reactivation test (DL-EPR). The kinetics of precipitation in the two steels was different due to the difference of the grain sizes. The results show a correlation between the sensitization degrees, measured by DL-EPR, with the amount of deleterious phases precipitated.
Highlights
Duplex (DSS) and superduplex stainless steels (SDSS) are materials used extensively in petrochemical industries due to elevated mechanical strength and high pitting corrosion resistance[1]
It can be be observed that the aging time necessary to reach the limit of Ir/Ia = 0.05 is lower in the SD-A specimens than in SD-B steel specimens
The main conclusions are: The double loop electrochemical potentiodynamic reactivation test (DL-EPR) test for both steels analyzed was optimized by the use of an electrolyte of 2.00 M H2SO4 + 0.01 M KSCN + 0.5 M NaCl solution at 40 °C
Summary
Duplex (DSS) and superduplex stainless steels (SDSS) are materials used extensively in petrochemical industries due to elevated mechanical strength and high pitting corrosion resistance[1]. Lopez et al.[12,13] analyzed the influence of σ phase precipitation on corrosion resistance in a DSS UNSS31803 sample aged at 675 °C and 900 °C by DL-EPR testing using a 2.00 M H2SO4 + 0.01 M KSCN + 0.50 M NaCl solution at 30 °C These authors considered the material susceptible to intergranular corrosion when the degree of sensitization (DOS=Ir/Ia) was greater than 0.0512,13. Pardal et al.[3] analyzed the DOS behaviour in specimens of 2505 SDSS obtained by different continuous cooling treatments Both researches were performed using the same solution proposed by Lopez et al.[12,13] using a scan rate of 1 mV s–1. Of interest was the comparative analysis of two SDSS with similar chemical compositions, but different grain sizes
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