Effects of interfacial stress on oxidation of mild steel

The effects of a compressive stress on the oxidation rate of mild steel have been investigated through the use of novel equipment designed to measure the extension of specimens during scaling. Preliminary results are described for mild steel oxidised in 2% CO-CO2. The rate of breakaway scaling is found to be lower at constrained interfaces by comparison with the free surfaces of the specimens and the rate of oxidation is shown also to decrease as the interfacial stress increases. The microstructures of the various breakaway scales formed with and without an external load, as examined in cross-section in the transmission electron microscope, are also described and possible reasons to account for the observed reduction in the oxidation rate are discussed. (author)