FE OXYCHLORIDE DESORPTION FROM AN FE POLYCRYSTALLINE SURFACE

We report the formation of an Fe oxychloride species at the surface of an O- and Cl-covered Fe polycrystalline surface below 230 K under UHV conditions. Our data show that FeOCl (amu 107) desorbs at 230 K. For FeCl2 (amu 126) desorption, two desorption peaks are observed at 230 a nd 620 K in the presence of chemisorbed oxygen. In the absence of oxyg en, only one FeCl2 desorption peak at 620 K is observed. Auger electro n spectroscopy and temperature programmed desorption studies reveal th at the reaction leading to Fe oxychloride formation involves dissociat ively adsorbed O and Cl at the Fe surface. These results indicate that chemisorbed or low coordinate oxygen plays an important and previousl y unsuspected role in chlorine-induced corrosion at ferrous surfaces.