The Influence of Chromium on the Passivation of Fe₃Al Iron Aluminides, Investigated Via Potentiodynamic Polarization in 0.25 M H₂SO₄

The influence of chromium on the passivation of Fe₃Al iron aluminides has been investigated by utilizing potentiodynamic polarization in freely aerated 0.25 M H₂SO₄. The selected alloys included a binary Fe-26Al, a ternary Fe-25Al-5Cr, and an austenitic stainless steel (X8CrNiS18-9). The iron aluminides underwent x-ray diffraction analysis and grain size investigation to confirm the independent influence factor of chromium on the obtained electrochemical data. Both iron aluminides exhibited extensive passivation ranges with decreased passive current densities in comparison to the investigated stainless steel. Furthermore, all three alloys illustrated a transformation of the passive layer during polarization. A mechanistic explanation for this passivation transformation for both iron aluminides is discussed and evaluated.