The Effect of Replacing Molybdenum with Vanadium on the Corrosion Resistant Properties of Stainless Steels

Abstract

The effect of replacing molybdenum with vanadium, both fully and partially, on the corrosion resistant properties of wrought ferritic, and wrought and cast austenitic stainless steels is examined. All alloys contained approximately 18% chromium with the austenitic alloys based on Types 304L and CF–8 respectively. The ferritic alloys contained chromium and 1–4% vanadium; the wrought austenitic alloys up to 6% vanadium and 2% molybdenum (not in combination); and the cast austenitic alloys up to 6% vanadium and 1.5% molybdenum, separately and in combination. Corrosion testing involved anodic polarization in H2SO4 and determination of the pitting potential in 0.lN NaCl. Vanadium was found to improve the pitting resistance of all alloys in NaCl, and generally had a beneficial effect on the passivation characteristics of the ferritic and wrought austenitic alloys in H2SO4. The element had a detrimental effect on passivity in the cast austenitic alloys, a fact possibly related to the higher carbon and nitrogen level and the formation of detrimental precipitating phases (e.g. carbides). Molybdenum was found to be more effective than vanadium on a weight-for-weight basis in conferring corrosion resistance.