High-Temperature Heat-Treatment at 1673 K: Improvement of Pitting Corrosion Resistance at Inclusions of Type 304 Stainless Steel under Applied Stress

Abstract

MnS inclusions in Type 304 stainless steel were mainly transformed into oxide/oxysulfide inclusions by heat-treatment at 1673 K. In 0.1 M MgCl₂ under both the no-stress and stress conditions, the pitting potential of the steel heat-treated at 1673 K was higher than the steel heat-treated at 1373 K. The pitting potential of the stainless steel heat-treated at 1673 K did not decrease due to applied stress. For the steel heat-treated at 1673 K, the dissolution current of oxide/oxysulfide inclusions was lower than that at MnS inclusions. The results show no significant decrease in the pitting potential of the steel heat-treated at 1673 K even under applied stress.

Fig. 2 Anodic polarization curves of the steel heat-treated at 1373 K or 1673 K in naturally aerated 0.1 M MgCl₂ at 298 K (a) without and (b) with stress. The electrode areas were 1.0 mm².