The corrosion behaviour of amorphous Fe-Cr-13P-7C, Fe-Cr-13P-7B and Fe-Cr-20B alloys in 9M H2SO4 solution at 30°C was investigated. An increase in the alloy chromium content improved the corrosion resistance of the amorphous Fe-Cr-13P-7C and Fe-Cr-13P-7B alloys. When only B is contained as a metalloid, alloying with chromium up to 15 at% is ineffective in increasing the corrosion resistance. The addition of phosphorous accelerates the cathodic reaction of hydrogen evolution on the amorphous Fe-Cr alloys.This leads to sharp ennoblement in the corrosion potential of amorphous Fe-8Cr-13P-7M (M = C,B) alloys from the active state to the passive state with immersion time, while the corrosion potential of Fe-8Cr-20B alloy is unchanged. Chromium is concentrated in the passive film on the amorphous Fe-8Cr-7M (M = C,B) alloys formed by immersion in 9M H2SO4 solution, and is further concentrated by prolonged immersion. In particular, the concentration of chromic ions in the passive film on the Fe-8Cr-13P-7C alloy is higher than in the film on the Fe-8Cr-13P-7B alloy.
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|Published - 1993 Nov