Effect of heat-affected zone on electrochemical corrosion behavior of welded joint with multi-metallographic structure zone

The welded joint is a multi-metallographic structure zone composed of the weld metal, the heat-affected zone, and the base metal. Most current research on welded joints primarily focus on the weld metal and base metal. Even when the heat-affected zone is considered, the discussion is mostly limited to corrosion test results, lacking in-depth analysis of corrosion behavior from an electrochemical perspective. To clarify the electrochemical corrosion process of multi-microstructure structures in welded joints, electrochemical tests were conducted to obtain the electrochemical parameters of each metallographic structure. A corrosion finite element model was established based on the microstructure morphology of each metallographic structure, and the validity of the finite element model was verified through corrosion tests. The influence mechanism of the heat-affected zone in the corrosion process of welded joints was elucidated. The effect of the width ratio of the heat-affected zone to the weld zone on the corrosion rate was analyzed. The results show that the multi-metallographic corrosion model of welded joints based on surface morphology can effectively reflect the real corrosion situation. The effect of the heat-affected zone on the corrosion behavior of welded joints is mainly reflected in the change of potential difference and the change of potential distribution in the weld zone. With an increase in the width ratio between the heat-affected zone and the weld zone, the difference in current density at the boundaries of each metallographic structure decreases, and the corrosion morphology becomes closer to uniform corrosion.