Pitting corrosion of U-bend hot-rolled 2205 duplex stainless steel under wet–dry cycling condition

Abstract

The pitting corrosion of U-bend hot-rolled 2205 duplex stainless steel (DSS) was investigated under wet–dry cycling conditions and compared with that of as-received one. After U-bending deformation, the average critical relative humidity (RH) for pitting corrosion during drying (RH_pit) increased from 49.4% to 56.9%, and the average critical RH for repassivation during wetting (RH_rep) increased from 67.9% to 84.1% for the exterior surface. For the interior surface, the average RH increased to 60.9% (RH_pit) and 85.8% (RH_rep), respectively. The increase in critical RH indicated U-bending deformation led to decrease in pitting resistance, with the interior surface exhibiting particularly significant degradation. Compared to round-type pits for the as-received sample, the exterior surface of U-bend sample exhibited irregular stretched-type pits with preferential dissolution of the austenitic phase, whereas the interior surface displayed the deepest round-type pits without any phase preferential dissolution. The degradation of pitting resistance and the modification of pit morphology of U-bend hot-rolled 2205 DSS were discussed herein.