The sulphidation of metals and alloys

Abstract

There is considerable interest concerning the corrosion behaviour of many materials in sulphur-containing environments, since this forms the basis of an industrial problem of considerable magnitude. Because of the widespread natural occurrence of sulphur in fuels (whether solid, liquid, or gaseous) severe corrosion may arise when materials come into contact with hot combustion atmospheres derived from these fuels, as in superheaters, heat-exchangers, gas turbines, &c. Sulphur-contamination problems also arise in processing plants in the petroleum and chemical industries. In these situations the principal concern is the interaction between metals and alloys and hydrogen sulphide, sulphur dioxide, sulphur trioxide, or elemental sulphur itself. These gases may be present at variable partial pressures, either individually or as mixtures with the additional components air, or nitrogen or oxygen, or combustion products, e.g. CO₂, CO, at elevated temperatures of up to 1200°C. Metal/alloy reactions with other sulphur-containing compounds such as carbon disulphide are also a source of concern. Interaction with sulphur dioxide (and/or trioxide) may produce scales consisting of the oxide alone, or oxide + sulphide, or even sulphate, but in the present review the reactions that lead to the formation of sulphide scales on metals and alloys only will be considered.