Corrosion behavior and mechanical performance of weathering steel in industrial and rural atmospheric environments

In this study, a series of alternate immersion tests were conducted to simulate the corrosion processes of weathering steel and control material (Q235 steel) in industrial and rural atmospheric environments. The corrosion rates of the two steels were regularly monitored and compared using weight loss method. Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) were employed to analyze the microstructure and phase compositions of the rust layer formed on steel. Finally, the tensile tests were performed to examine the mechanical performance degradation of weathering steel. The results indicated that the corrosion rates of weathering steel decreased dramatically at first and then tended to be steady. In industrial environment, the weathering steel maintains a 30 % lower corrosion rate than Q235 steel, whereas in rural environment, the difference between the two corrosion rates decreased dramatically over time and disappeared after 360 h. The cause for the difference between the corrosion rates is that weathering steel has higher content of alpha-FeOOH, CuO and Ni compounds in the corrosion product which make its rust layer more compact and denser than that of Q235 steel, leading to better corrosion resistance. Existing stress-strain curve models for ordinary steel gave poor prediction effect in the hardening stage of weathering steel. Therefore, a new constitutive model for the weathering steel was proposed in this study. It is demonstrated that the proposed model can well reflect the mechanical behaviors of weathering steel before and after corrosion.