Electrochemical Corrosion Behavior Of Oxidation Layer On Fe30mn5al Alloy

The Fe30Mn5Al alloy was oxidized at 800 degrees C in air for 160 h, the oxidation-induced layer about 15 mu m thick near the scale-metal interface was induced to transform to ferrite and become enriched in Fe and depletion in Mn. The effect of the oxidation-induced Mn depletion layer on the electrochemical corrosion behavior of Fe30Mn5Al alloy was evaluated. The results show that in 1 mol . L-1 Na2SO4 solution, the anodic polarization curve of the Mn depletion layer exhibits self-passivation, compared with Fe30Mn5Al austenitic alloy, and the corrosion potential E-vs (SCE) is increased to -130 mV from -750 mV and the passive current density i(p) is decreased to 29 mu A/cm(2) from 310 mu A/cm(2). The electrochemical impedance spectroscopy (EIS) of the Mn depletion layer has the larger diameter of capacitive arc, the higher impedance modulus vertical bar Z vertical bar, and the wider phase degree range, and the fitted polarization resistant R-t is increased to 9.9k Omega . cm(2) from 2.7k Omega . cm(2) by using an equivalent electric circuit of R-s-(R-t//CPE). The high insulation of the Mn depletion layer leads to an improved corrosion resistance of Fe30Mn5Al austenitic alloy.