Corrosion and passivation of amorphous and crystalline Fe- Cr alloys in ethanol/water/HCl mixtures

The corrosion and passivation of Type 304 SS and of the amorphous alloys Fe-10Cr-13B-7C and -13P-7B, respectively, have been studied by polarization curves and impedance spectroscopy in deaerated ethanolic/0.5 N HCl solutions with different water contents. For stainless steel and the 13B-7C amorphous alloy, the same passivation mechanism is effective as in aqueous media. The water molecules are directly involved in the formation of the passive film. The alloy with 13% phosphorus appears to show two separate regions of film formation: at low potentials, a thick, porous and less protective film is formed than at more noble potentials. The synergistic interaction of chromium, water and metalloids in film formation may be explained with the concept of charge/size ratio of the different dissolution products