SURFACE-ANALYSIS OF PASSIVE STATE

The principles of the ESCA and the Auger-techniques are described and a method for quantitative ESCA analysis of passive film is presented. The method is exemplified by an analysis of the passive film formed on stainless steel (20Cr18Ni6MoO.2N) during polarization in 0.1 M HCl + 0.4 M NaCl. The thicknesses of the passive films formed at -100 mV and 500 mV (SCE) are 13 Å and 15.5 Å respectively. The film consists of an inner FeCr oxide phase and an outer monolayer of Cr(OH)3. The average cation content of Cr3+ in the inner oxide is about 50%. Variable angle analysis shows that the Cr3+ content is higher at the metal interface than at the outer interface. Mo6+ is enriched in the outer layer. The content of Mo4+ in the oxide layer decreases with the potential. The Ni2+ content in the passive film is low. Chloride ions are dissolved in the oxide as well as in the hydroxide layer. A stationary state is reached within 2 min. © 1990.