Corrosion behavior of Q235 steel in tropical marine atmosphere of Hainan Island
Shanli Qin, Sifan Li, Xin Wang
Abstract
This paper investigates the corrosion behavior of Q235 steel in tropical marine atmosphere of Hainan Island by natural and accelerated exposure tests. The accelerated tests were conducted with employing water spray, seawater spray and salt spray, respectively. The corrosion morphology and products were characterized. The time-dependent evolution of corrosion depth and mechanical properties of Q235 steel were studied. A grey correlation analysis was performed to correlate the corrosion depths under accelerated and natural conditions. Finally, the constitutive models of corroded steel were refined. The results show that corrosion kinetics of Q235 steel follows a “power function–linear function” model. After 24 months of exposure, the corrosion depths were 58 μm, 533 μm, 780 μm, 853 μm and 904 μm for natural exposure, water spray, seawater spray, 3.1 % salt spray and 5 % salt spray conditions, respectively. The correlation coefficients between corrosion depths under natural and various accelerated conditions all exceeded 0.65. Mechanical properties degraded following a power function trend with exposure time. Notably, the yield plateau with a length of approximately 0.0158 in the stress-strain curve abruptly disappeared when the corrosion ratio exceeded an average critical corrosion ratio of 22 %. The multi-linear model (MLM) proved concise and practical, while the quadratic plastic flow model (QPFM) offered higher accuracy. The revised MLM provided an improved fit to the experimental data, and the revised QPFM effectively optimizes the fitting for the cases exhibiting a yield plateau.