The study on in-situ corrosion of the galvannealed coating under AFM in solution

摘要

In this article, the phase composition of hot dipped galvannealed (GA) coating was investigated via chemical exfoliation method; the morphology changes of the GA coating during the corrosion process were observed, and the dissolving characteristics were studied. Then atomic force microscope (AFM) was introduced to study in-situ corrosion of GA coating in solution and analyze the corrosion mechanism in nano-scale. The results indicated that compressed structures were generated on the surface of GA coating during the finishing, which was the initial stage of corrosion caused by the residual stress on the surface. Secondly, compared with other parts of the binary alloy phase, the bulge tip was firstly corroded in the medium, resulting in a continuously decreasing of surface roughness. Thirdly, the corrosion of metals were not only related to their equilibrium potentials but also related to their surface structures. Smooth and flat surfaces tended to be more resistant to corrosion than rough surfaces.