A Flexible Reference Array Electrode Technique for In Situ Imaging the Corrosion of Q235 Carbon Steel Welded Joints

Introduction: Localized corrosion in welds has always been a very common and difficult problem in many industrial fields. Preferential corrosion usually occurs in the weld zones with irregular shapes of metal welds due to the welding process. Methods: To address the challenge of monitoring corrosion behavior at the weld zone in real-time, a novel Ag/AgCl flexible array, arranged in a 4×8 electrode configuration, has been developed. This array is employed for in situ monitoring of the corrosion process in Q235 steel welded joints (including single butt welds, double butt welds, and fillet welds) immersed in a 0.01 mol/L NaCl solution with a pH of 9. The measurement is conducted using a custom-made array electrode signal test system. Results: The results demonstrate that the prepared electrode exhibits a highly responsive behavior to chlorine ions from 0.001 to 0.1 mol/L concentration and maintains excellent stability during 4000s. The weld zone shows higher corrosion activity and trends to generate pitting corrosion for all three welded joints in the first 15 min. With the increase of time, micro pitting corrosion dissolves and expands to macro point corrosion in the next 30 min. Conclusion: The flexible reference array electrode proves to be a powerful tool for the in situ monitoring of carbon steel corrosion, offering a comprehensive depiction of the steel's corrosion status over time. Such insights are crucial for making accurate corrosion predictions and conducting service life evaluations of steel structures.