Surface spectroscopic study of the corrosion of ultrathin Fe-57-evaporatedand Langmuir-Blodgett films in humid SO2 environments

Integral conversion electron Mossbauer spectroscopy (ICEMS), x-ray photoele ctron spectroscopy (XPS), Auger electron spectroscopy (AES) and scanning el ectron microscopy (SEM) have been used to carry out a comparative study of the corrosion resistance against humid SO2-aggressive environments of ultra thin Fe-57 films, These films, having a thickness less than or equal to 2.5 mn, have been prepared by evaporation of Fe-57 under vacuum and by Fe-57 c oating by a Langmuir-Blodgett (LB) technique on SiO2/Si wafers. The results have shown that the corrosion resistance of the evaporated hams is similar to that of massive Fe, However, the LB films show a remarkably higher corr osion resistance, Thus, although the Pe films prepared by evaporation have been completely corroded after 6 h of exposure to the deleterious environme nt, tate EB films remain unaltered even after 18 h of exposure to the same aggressive conditions. The higher corrosion resistance of the LB films appe ars to be related to the existence of a thin surface layer containing Si, F e2+ and Fe3+ formed on top of the Fe metal him during the thermal treatment s subsequent to the LB deposition. Copyright (C) 2000 John Wiley & Sons, Lt d.