EFFECT OF ADSORBED OXYGEN ON THE KINETICS OF CHEMICAL-REACTIONS ON METAL-SURFACES

The effects of adsorbed impurities on the kinetics of reactions on metal surfaces are discussed, in particular the reactions of water vapor and carbon dioxide with iron surfaces are analyzed. The critical oxygen potentials for the onset of 'poisoning' of the reactions appear to correspond with the onset of facetting of iron and the formation of surface phases on the iron. The maximum chemical reaction rate constants for the reactions of water vapor and of carbon dioxide on iron surfaces at a given temperature are shown to correspond closely to the chemical reaction rate constants determined from the reduction of iron oxides in their respective systems. The phenomena observed on the reaction of gases with iron and iron oxide surfaces are reported in other metal systems thus the analysis used for the present reactions appears to be applicable to other systems involving metal/gas reactions. © 1979 American Society for Metals and the Metallurgical Society of AIME.