Effect of Chlorine and of H 2 S on the Oxidation Resistance of Various Austenitic Stainless Steels

Abstract

Studies were made on the oxidation resistance of austenitic stainless steels type AISI 304, 320, 316, and 321 in humid oxygen at 30 torr (4 kN/m²) at 950°c and at 650°c, for 250 h infive 50 h cycles, and also on the effect of intermittent exposure of the specimens to Cl₂ or to H₂S during theoxidation experiment. In addition, the oxidation resistance of these steels in (95% O₂ + 5% Cl₂), (90%O₂ + 10%H₂S), and (85% O₂ + 5% Cl₂ + 10H₂S) was also studied. Intermittent exposure to Cl₂ or to H₂S damaged the protective oxide layersand increased the rate of oxidation. Attack in (95% O₂ + 5% Cl₂ at 950°c was found to be extremely severe and the test had to be terminated after a short period; however, oxidation in (90% O₂ + 10% H₂S) at 950°c drastically reduced the rates for all the steels. Tests in (85% O₂ + 5% Cl₂ + 10% H₂S) at 950°c exhibited an intermediate type of attack. Oxidation rates of various steels in wet O₂ at 650°c were much lower than those at 950°c, and the intermittent exposure to Cl₂ or to H₂S accelerated the attack. Rates of oxidation in (90% O₂ + 10% H₂S) at 650°c were even lower than those for oxidation in wet O₂, Under all the conditions, the resistance to oxidation or corrosion of the various steels tested was in the order: 310 > 316 > 304 > 321.