Experimental study on the mechanical property degradation of different regions in corroded cold-formed thick-walled square steel tubes

This study experimentally investigates the effects of corrosion on the mechanical properties of the flat, weld and corner regions of cold-formed thick-walled square steel tubes. A total of 20 corroded tensile coupon specimens with different corrosion levels were prepared through accelerated corrosion tests. Three-dimensional surface morphology scanning and monotonic tensile tests were subsequently conducted to characterise the corrosion morphology, damage parameters and mechanical-property degradation of different regions. The test results show that significant differences exist in the corrosion morphology characteristics and mechanical-property degradation behaviours among the flat, weld and corner regions. With increasing corrosion severity, the corner regions exhibited the most pronounced strength degradation. At a corrosion ratio of 7.59%, the yield strength and ultimate strength of the corner regions decreased by 16.6% and 14.0%, respectively. In contrast, the weld regions exhibited a more pronounced reduction in elongation at fracture, with the elongation decreasing by 36.9% at a corrosion ratio of 7.59%. Based on the test results, prediction models for the residual material strength of different regions of corroded cold-formed thick-walled square steel tubes were developed, and the predicted results showed good agreement with the experimental data. The findings provide a reference for evaluating the residual material properties of corroded cold-formed thick-walled square steel tubes.