The corrosion processes and mechanisms of Q235A steel under wet-dry cyclic condition were studied using polarization curve compared with immersion samples, while, the corrosion morphologies and corrosion products of the steel samples were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The cathodic process of wet-dry samples was likely to be controlled not by the oxygen reduction, but rather by the reduction of corrosion products. During the drying process of the wet-dry sample, the electrolyte thickness decreased and chloride concentration increased. Oxygen would be much easier to diffuse into the interface of electrolyte/metal, which improved the cathodic reduction processes. Except for this, the rust itself took part in the reduction processes and hence increased the corrosion rate of the steel samples.
