Electrochemical corrosion behavior of welded joints with multi-metallographic structures in liquid film electrolytes

Welded joints in steel structures demonstrate significant corrosion susceptibility in atmospheric environments due to their multi-metallographic structures. Current research predominantly focuses on the galvanic couple formed between the weld metal and base metal, yet critically neglects the effect of the heat-affected zone. Moreover, the electrochemical corrosion mechanisms under atmospheric liquid film electrolyte conditions remain insufficiently investigated. To elucidate the electrochemical corrosion characteristics of welded joints with multi-metallographic structures under liquid film electrolytes, we developed a three-electrode corrosion model incorporating mass transport and corrosion products. By implementing controlled variations in liquid film thickness and corrosion product porosity, the study examined the dynamic evolution of the electrolyte film and electrode surface reaction kinetics during corrosion processes. The results indicate that the corrosion process of the weld seam and base metal is always jointly controlled by electrode reactions and oxygen diffusion, while the heat-affected zone is co-regulated by liquid film thickness and corrosion product porosity. An increase in liquid film thickness and porosity can promote ion diffusion and reduce the potential difference, thereby decreasing the acidification difference between different metallurgical structures in the welded joint. As the porosity increases, the corrosion morphology of each metallurgical structure gradually becomes more uniform.