Study on the corrosion behavior of hot-dip galvanized steel in simulated industrial atmospheric environments

In this paper, the corrosion behavior of hot-dip galvanized steel in simulated industrial atmospheric environment was studied by accelerated salt spray test. The results were compared with the immersion test to obtain the characteristics of atmospheric corrosion. Firstly, the micro-morphology of the zinc layer and corrosion product layer on the surface of hot-dip galvanized steel was observed by SEM and EDS. Then, the phases of hot-dip galvanized steel in different corrosion cycles were analyzed by XRD diffraction patterns and FTIR infrared spectroscopy. Finally, electrochemical tests were conducted to compare the electrochemical parameters of hotdip galvanized steel under different corrosion cycles in order to study the differences in corrosion rates at different corrosion stages. The results indicate that the main product of salt spray corrosion is ZnO, and it contains a small amount of Zn5(CO3)2(OH)6 and Zn4(OH)6SO4. The above corrosion process can be divided into three stages, and the corrosion mechanism is consistent with the experimental phenomenon. Specifically, as corrosion develops, the corrosion product layer becomes denser, improving the corrosion resistance of hot-dip galvanized specimens. However, the corrosion products on the surface are looser in the immersion test. When the corrosion time increases, corrosive media is prone to invade the galvanized layer, resulting in pitting corrosion.