Effect of cobalt on the corrosion behaviour of amorphous Fe-Co-Cr-B-Si alloys in dilute mineral acids

Abstract

The aim of this paper was to investigate the effect of increasing cobalt content on the corrosion resistance of the Fe-Co-Cr-B-Si alloys in dilute mineral acids. The corrosion rates in 0.5N HCl, 1N HCl and 1N H 2SO4 significantly decrease with an increase in cobalt content. The alloys with a larger amount of cobalt can passivate spontaneously. The high corrosion resistance of the Fe-Co-Cr-B-Si alloys is also due to the formation of chromium-enriched passive film. Generally, the corrosion resistance of chromium-bearing alloy is improved by alloying with various metalloids but it is lowered by addition of boron and silicon. The corrosion behaviour of the amorphous Fe75-xCoxCr1B7Si 17 alloys obtained by the melt-spinning technique was studied using gravimetric method. The best results were obtained with Fe65Co 10Cr1B7Si17 alloy. The studied amorphous alloy ribbons exhibit not only excellent physical properties which are useful for many electric and magnetic applications: magnetic sensors, power transformers, high frequency transformers, etc., but also a very good corrosion resistance which extend their application domain.