Degradation of mechanical properties and constitutive model of stainless steel under corrosion environment

This study systematically investigated the corrosion damage evolution and mechanical property degradation mechanisms of Q345 steel, 316L austenitic stainless steel, and 2205 duplex stainless steel. A 2000-hour copper-accelerated salt spray test was conducted. The results reveal distinct differences in corrosion morphology and degradation mechanisms among the three steels. Q345 steel undergoes uniform corrosion, leading to a continuous degradation pattern. In contrast, both stainless steels are characterized by localized pitting corrosion, with 2205 duplex stainless steel exhibiting the highest pitting resistance owing to its duplex microstructure and greater alloy content. Mechanical tests demonstrate a decline in both strength and ductility with prolonged exposure. Q345 steel suffers the most severe degradation in mechanical properties, while 2205 duplex stainless steel maintains the best mechanical stability. Based on the experimental data, a corrosion damage variable is introduced into classical constitutive models, leading to the development of a time-dependent dual-hardening model and a Ramberg-Osgood model. Validation analysis indicates that the piecewise-function-based dual-hardening model characterizes the mechanical response of corroded materials during both the hardening and necking stages more accurately than the Ramberg-Osgood model, with an average prediction error only one-quarter of the latter. The established corrosion constitutive relationship provides a critical theoretical and modeling basis for assessing the durability and performing numerical simulations of steel structures in corrosive environments.