Corrosion of iron–aluminium alloys in gaseous atmosphere containing hydrogen chloride and hydrogen sulphide at 600 and 700°C

Abstract

The corrosion of two binary iron–aluminium alloys was compared in gaseous CO₂–H₂–HCl–H₂S and CO₂–H₂ mixtures at 600 and 700°C. In each environment, the Fe–14Al alloy resisted corrosion due to the formation of a protective alumina scale. The Fe–4Al alloy corroded more rapidly in the CO₂–H₂–HCl–H₂S atmosphere than in the CO₂–H₂ atmosphere at both temperatures. The corrosion products comprised thick outer layers of iron oxide, porous inner layers of mixed iron–aluminium oxide and internal precipitates of aluminium oxide. Sulphur was detected near the scale/alloy interface and the increase in corrosion rate was attributed to the presence of chlorine and sulphur.