Coupled Response Surface Methodology-Multiphysics Modeling of Salt Spray Corrosion in 16Mn Steel for Offshore Platforms

The corrosion behavior of 16Mn steel knee plates under marine salt-spray conditions was investigated using a coupled experimental and finite-element modeling approach. Controlled salt-fog exposures varying humidity, chloride concentration, and applied tensile stress were performed and analyzed by a Box-Behnken design to quantify main and interaction effects. Electrochemical measurements yielded corrosion current densities that were used to develop a quadratic prediction model via response surface methodology (RSM). Finite-element simulations reproduced local stress concentrations and electrochemical fields, and identified right-angled corners and curved edges as zones of localized severe attack. Statistical analysis indicates that ambient humidity is the dominant factor influencing corrosion rate, with a significant humidity-stress interaction. The regression model achieved R2 = 0.9841, demonstrating strong agreement with experiments. These results clarify the coupling mechanism between environmental and mechanical factors and provide a practical predictive tool for optimizing material selection, geometric design, and maintenance prioritization for offshore structural components.