Evaluation of Intergranular Corrosion Susceptibility of Aged Super 304H Stainless Steel

Double loop potentiokinetic reactivation method was used to investigate the intergranular corrosion susceptibility of super 304H steel which was subjected to aging treatment at 650 ℃. The results showed that intergranular corrosion occured due to the precipitation of M23C6 along grain boundaries. With the change of aging time, the precipitating rate and amount of M23C6 precipitated along grain boundaries varied accordingly. M23C6 precipitated rapidly at the initial stage, which led to the rapid increase of intergranular corrosion susceptibility. With the increas of aging time, the amount of M23C6 precipitates increased accordingly. This resulted in the increase of intergranular corrosion susceptibility. The increasing rate of intergranular corrosion susceptibility is related to the increasing rate of M23C6 precipitates. Depletion of Cr caused by precipitation of M23C6 along grain boundaries leads to the occurrence of intergranular corrosion, and the precipitation of M23C6 inside the grains also results in the formation of Cr-depleted zone and the subsequent corrosion.