Effect of the heat treatment on the corrosion behaviour of amorphous Fe–Cr–P–C–Si alloy in 0.5 M H2SO4

The effect of the heat treatment on the corrosion behaviour of amorphous Fe85Cr5P6C3Si alloy in 0.5 M H2SO4 has been investigated using electrochemical techniques. Heat treatment was carried out at temperatures varying between 250 and 650 8C at different times 30, 60, 120 and 240 min. The evolution of crystallization processes after annealing was identified by differential thermal analysis (DTA) and by X-ray diffraction (XRD). The diagrams obtained by DTA show that the structure of samples treated at high temperature changes towards a crystalline state. This crystallization phenomenon is confirmed by the analysis with the XRD. The results obtained from the polarization curves reveal that for all the studied temperatures of annealing, Fe–Cr–P–C–Si exhibits a phenomenon of passivation without breakdown of passivity. The best corrosion resistance is obtained at the temperature of annealing 350 8C. For an annealing at higher temperatures, Fe85Cr5P6C3Si becomes less corrosion resistant than same amorphous alloy treated with temperatures lower than 350 8C.