X-RAY PHOTOELECTRON SPECTROSCOPIC STUDY OF THE PASSIVITY OF FERRITIC 19CR STAINLESS-STEELS IN 1-NHCL

The composition of surface films formed on 19Cr and 19Cr-2Mo ferritic stainless steels in 1N HCl has been analyzed by X-ray photo-electron spectroscopy. The composition of the passive films on both steels is essentially the same. Passivation takes place by the formation of a hydrated chromium oxy-hydroxide It has been suggested that, in general, the passive film is not uniform but contains micro-pores which are repeatedly formed and repassivated. The roles of chromium and molybdenum in increasing the corrosion resistance have been illustrated in terms of the activity and repassivation of micro-pores The origin of the micro-pores has also been suggested. © 1979.