Effect of the steel substrate on the composition of gases in enameling

The gas phase occupying up to 40 vol% of a vitreous enamel coating largely determines the most important properties, such as density, impact strength, adhesion, etc. An attempt was made to identify and determine the amount of gases emitted from the bulk of the steel substrate, desorbed from the surface, and formed as a result of its interaction with air in heating during the enamelling process. Variations in the composition of the gas phase (H2; O2; steam; CO; CO2) in heating St.3 steel substrates in air are plotted, and the results are discussed. The effect of the substrates on the composition of the gas bubbles in the vitreous enamel coating was established. It is shown that the substrates are a source of CO, steam and H2 emission. The reactions occurring are shown and discussed. 2 refs.