The corrosion behaviour of iron-chromium alloys in 0.5 M sulphuric acid

The corrosion of five different iron-chromium alloys was studied in 0.5 M H2SO4, using polarization curves and impedance measurements. The data obtained were compared with the data obtained for pure iron and chromium. It was concluded that the passive current density for the alloys with a Cr content ≤9% is diffusion controlled. For alloys with a higher Cr content, 13 ≤Cr% ≤ 25, and the pure metals this is not the case. The passive film on the lower alloyed iron-chromium alloys is a porous film just after the active-passive transition. This porosity decreases with increasing chromium content and/or potential improving the protective quality of the film.