Abstract:The intergranular corrosion of 304 stainless steel was evaluated by electrochemical potentiodynamic reactivation (EPR) combined with scanning electron microscopy (SEM) and metallographic microscopy. The release of chromium ions from 304 stainless steel specimens at different degrees of sensitization and the effects of the time and temperature of immersion on chromium ion release from specimens at the same degree of sensitization were studied. The results showed that 304 stainless steel could avoid intergranular corrosion, which annealed at a low temperature. As annealing temperature increased from 500 ℃ to 650 ℃, the corresponding degree of sensitization also increased. The specimens suffered severe intergranular attack after being exposed at 650 ℃. While the annealing temperature continued to increase, chromium depletion weakened, and sensitization decreased. With the increase in the degree of sensitization, chromium ion precipitation increased in acid solutions as well. However, there was no effect of the degree of sensitization on chromium ion release in neutral chlorine solution. In different soaking solutions, the immersion time had different degrees of impact on the self-corrosion potential of the specimens, resulting in changes in resistance of specimens to corrosion. The increase in immersion temperature accelerated the corrosion of sensitized specimens, leading to a sharp increase in chromium ion precipitation.
