Possible mechanisms for the transport of sulphur through oxide scales

Certain previously unobserved features of scale formed in an oil‐fired billet reheating furnace are described. It is shown that sulphur‐rich melts formed at the scale/metal interface penetrate the grain boundaries of the overlying scale: subsequently the sulphur is removed by an oxidation reaction in which the surrounding manganese‐containing oxide takes part, to form a complex manganese silicate. The thermodynamics of possible reactions are discussed briefly and hypotheses put forward for the transport mechanisms of sulphur from the furnace atmosphere to the scale/metal interface.