Experimental investigation on the evolution of static and hysteretic properties of structural steel after 25 years atmospheric corrosion

Abstract

Long-term atmospheric corrosion poses a significant challenge to the safety and durability of steel structures. This study investigates the long-term deterioration mechanisms and mechanical performance of Q355 steel subjected to 25 years of natural atmospheric corrosion. Surface morphology scanning, monotonic tensile tests, and cyclic loading tests were conducted to quantify corrosion-induced degradation and to develop corresponding constitutive models. Linear relationships were identified between roughness parameters, expected pit depth (h_pit), and the mass-loss rate (ρ_m). Notably, when ρ_m exceeds 8.02%, h_pit under atmospheric exposure grows markedly faster than in the continuous neutral salt spray (CNSS). Monotonic tensile tests revealed a transition from ductile (Grades I–II) to brittle fracture (Grade III) with increasing corrosion severity, and linear degradation equations were derived for strength and deformation indices as functions of ρ_m. A modified trilinear static constitutive model incorporating a corrosion-dependent factor was proposed, improving strain-hardening accuracy by up to 47.31%. Under cyclic loading, the energy dissipation coefficient (E_n) decreased linearly with ρ_m, while cyclic softening and strain-hardening indicators exhibited exponential degradation. A hysteretic constitutive model accounting for both ρ_m and cyclic strain was further established and calibrated. Comparisons with experimental results confirm that the proposed framework accurately reproduces the hysteretic behavior of atmospherically corroded steel, providing a reliable basis for structural performance assessment under long-term corrosion.