Effect of Microcracks on the Corrosion Behaviour of Fe-based amorphous coatings in Chloride Solutions

In this paper, the influence of microcracks on the corrosion behaviour of Fe-based amorphous coating on 304 stainless steel in 3.5 wt.% NaCl solution was investigated. Results show that microcracks deteriorate the corrosion resistance. The corrosive solution can penetrate into the microcracks, resulting in the direct corrosion of the substrate. Furthermore, the pitting potential of the substrate at the coating–substrate interface is apparently lower than that of the uncoated substrate, which is ascribed to the crevice corrosion caused by through-microcracks. As a result, the coated substrate is more prone to corrosion than the uncoated substrate. The microcracks can be effectively sealed by aluminium phosphate sealant, which improves the protectiveness of amorphous coating.