The Composition of Passive Films on Ferritic 30Cr Stainless Steels in H2SO4

X-ray photoelectron spectroscopy has been used to investigate the compostion of passive films formed on high purity, ferritic 30Cr stainless steels with and without molybdenum as a function of polarization potential. It has been found that the composition and thickness of passive film on the 30Cr-2Mo stainless steel are essentially the same as those on the 30Cr stainless steel and the film consists mainly of hydrated chromium oxy-hydroxide. A small amount of molybdenum exsists in the passive film on the 30Cr-2Mo stainless steel. The ratio of molybdenum to chromium in the film is smaller than that in the substrate steel.