Time and temperature dependence of the adhesion of oxide scales formed on phosphorus-containing steels during short term oxidation

The influence of phosphorus (0.15 wt.%) on iron oxide scale adhesion is studied for short time oxidation of carbon steel in air at 800 and 1000 °C. Adhesion is measured after cooling to room temperature by Vickers indentation. It is shown to increase with increasing oxidation time as the result of the formation of a phosphorus-containing phase at the steel–scale interface. It also exhibits much higher values after oxidation at 1000 °C than after oxidation at 800 °C. This is suggested to be due to molten oxide infiltrating the metal grain boundaries during oxidation at the highest temperature. The FeO–Fe3(PO4)2 eutectic temperature of 940 °C appears therefore as a critical parameter in the steel descaling process on the production line.