OXIDATION OF IRON SURFACE COVERED WITH SULFUR AND OR POTASSIUM

The oxidation process of a clean Fe(III) surface and that covered with sulphur and/or potassium has been studied. The sticking coefficient of oxygen decreases with increasing coverage of the iron surface with sulphur and it is about 10 times smaller for oxidation of the p(1 x 1)-S surface than for the p(1 x 1)-O one. The adsorbed oxygen atoms are located over sulphur atoms. The oxidation process occurs by diffusion of the iron atoms to the oxide surface through the monolayer of sulphur atoms. When oxygen is adsorbed on the iron surface covered with potassium, the oxygen atoms are located underneath the layer of potassium atoms. The sticking coefficient of oxygen on this surface is near 1 to reach the oxygen coverage near 1. The presence of potassium on the Fe(III) surface removes the inhibiting influence of sulphur on the oxidation process.