Stress corrosion and its mechanism of the hot-dip galvanized layer on steel structures in the simulated industrial pollution environment

Purpose This study aims to investigate the stress corrosion behavior and mechanism of the galvanized layer on steel structures commonly used in power grid equipment in the simulated industrial pollution environment. Design/methodology/approach In this work, Q235 galvanized steel plates, typically used in the steel structures of power grid equipment, were selected for the stress corrosion study of the hot-dip galvanized layer. A NaCl + NaHSO3 aqueous solution was prepared to simulate a corrosive industrial pollution medium, and a custom-designed three-point bending stress loading device was used to apply stress to the samples. The corrosion process was analyzed using a combination of scanning electron microscopy, X-ray diffraction and electrochemical detection methods. Findings The results demonstrate that the corrosion products with/without stress are primarily composed of ZnO, Zn4SO4(OH)6·5H2O and Fe(hydroxyl)oxides. The Ecorr and icorr of the stress samples are −1.2943 V and 259.5 µA⋅cm−2, respectively, while the nonstressed are −1.0922 V and 242.0 µA⋅cm−2. The applied stress induces grain boundary slip in the galvanized layer, leading to the destruction of its oxide film. Thereafter, it accelerates the formation and expansion of corrosion pits in the η-Zn layer, leading to the initiation of stress corrosion cracks, and further exacerbating the electrochemical corrosion of the galvanized layer. Originality/value The intrinsic connection between the microscopic process and macroscopic law of galvanized steel stress corrosion in a simulated industrial pollution environment is clarified. In addition, the stress corrosion mechanism is proposed, reflecting the correspondence between the microscopic process and macroscopic law.