The high temperature oxidation and - corrosion of irons and steels

This research has been concerned with the oxidation and corrosion of iron and mild steels, with particular reference to the importance of the mechanical properties of the surface oxides formed. A vibration technique has been used as the basic means of investigation, complemented by hot stage microscopy, thermobalance, microscopy, etc., where applicable. It has been found that the oxides formed on iron and steel become partially detached at the scale/metal interface continually during growth. This form of damage has been ,· found to have a profound effect on the dynamic modulus of the oxides, and on its behaviour under thermal shock or corrosive conditions. A particular EN2 steel has been found to be largely resistant to sodium chloride and sodium sulphate corrosion when preoxidised. This enhanced corrosion resistance has been attributed to the presence of a thin adherent oxide layer on the metal surface, whose adherence is due to the concentration of nickel in that region during oxidation. The vibration apparatus and specimens have been modified to enable tensile loading during oxidation such that the strains that a surface oxide is able to withstand before cracking may be measured. It has been found that the strains to fracture increases with increasing temperature. The application of the vibration technique in this role as a crack detection system has been shown to be very satisfactory.