Selective corrosion of duplex stainless steel bars in acid. Part 2: Effect of the surface strain and numerical analysis

Abstract

In the second part of this study, the effect of the strain level on the selective corrosion of the phases comprised in four different heavily strained duplex stainless steel (DSS) bars is analyzed. The corrosion behavior of the surface of bars with variable strain levels is analyzed and compared to the results of the less strained core of the same bars. For lean DSS bars (UNS S32304 and S32001 grades), an increase on the corrosion rate caused by the strains has been detected for the surface. For these DSS without Mo, ferrite has proved to be more sensitive to decrease on the corrosion resistance caused by the strain than austenite. In these cases, the strains expand the region of active corrosion toward higher potentials. On the other hand, when the grains are heavily strained parallel to the surface, if the most corrosion resistant phase has good corrosion behavior in the medium (UNS S32205 grades), the corrosion rate can be effectively slowed down, in spite of the microstructural defects.