Effect of ECAP and Heat-treatment on Pitting Corrosion Behavior of Industrial Pure Iron

Abstract

In order to guide a reasonable application of the bulk ultrafine-grained industrial pure iron, a serious of ultrafine-grained pure iron samples with different microstructures were fabricated by multi-passes ECAP and heat-treatment, and their microstructures and pitting corrosion behaviour were investigated by transmission electron microscopy (TEM), electrochemical polarization and impedance spectroscopy (EIS) techniques, respectively. Results show that:with the increase of ECAP passes, lath-shaped structure with high dislocation density transforms into equiaxed grains with low dislocation density; the dislocation density decreases and the high-angle grain boundaries increase, after the annealing treatment. ECAP passes have less effect on the self-passivation of pure iron, and its open circuit potential (OCP) and polarization resistance are less changed; the pitting corrosion resistance of the ECAPed pure iron is related to the ECAP passes:the pitting potential first decreases and then increases with the increase of ECAP passes; the self-passivation property and pitting corrosion resistance of the ECAPed pure iron are improved after the annealing heat-treatment, the OCP, polarization resistance and pitting potential values increase obviously.

Keywords

• ECAP
• heat-treatment
• industrial pure iron
• pitting corrosion behavior