Semi-empirical stress-strain Model of Structural Steels with Simulated Seawater Corrosion Damage

• Extends non-uniform corrosion damage to include retained corrosion damage layers and internal micro-defects, supported by SEM and nanoindentation evidence revealing progressive mechanical degradation. • Establishes a corrosion damage characterization framework by decomposing uniform and non-uniform components, with quantitative evolution models based on weight loss and power-law relationships. • Proposes a semi-empirical constitutive model incorporating initial corrosion damage and plastic damage evolution, enabling accurate prediction of full stress–strain behavior of corroded steels. • Demonstrates improved prediction accuracy for elastic modulus, yield strength, and ultimate strength, overcoming limitations of conventional secondary plastic flow models. • Provides theoretical basis and engineering guidance for mechanical performance evaluation and durability assessment of high-strength steels in marine environments. Seawater corrosion significantly degrades the mechanical properties of structural steels, posing challenges to accurately predicting the residual strength of marine steel structures. This study establishes a semi-empirical stress–strain model that incorporates both uniform corrosion damage and non-uniform corrosion damage to characterize the mechanical behavior of corroded steels. Experimental observations reveal the formation of a non-uniform corrosion damage layer accompanied by micro-defects and reduced hardness, whose evolution follows a power-law relationship with the weight loss rate. The proposed damage model quantitatively relates corrosion-induced damage to mechanical property degradation and integrates it into a unified constitutive framework. Model validation using Q345 ,Q690 and Q355B steels demonstrates that the predicted stress–strain curves agree well with experimental results, accurately capturing the reductions in elastic modulus, yield strength, and ultimate strength caused by corrosion. Compared with conventional models, the proposed approach improves prediction accuracy by explicitly accounting for microstructural corrosion damage. The model provides an effective tool for evaluating the residual mechanical performance and structural safety of corroded steel components in marine environments, offering practical significance for durability assessment and life prediction of marine steel structures.