Research on Corrosion Resistance and Fatigue Performance of Q420ENH+316L Clad Steel Butt Joints

To address the issue of long-term corrosion protection and durability enhancement for steel bridge decks， this study focus on Q420qENH+316L clad steel butt joints. Cyclic immersion corrosion tests were conducted in a 0.01 mol/L NaHSO₃ solution， combined with corrosion weight loss measurements and analyses of the rust layer's morphology and composition， the corrosion behavior and pitting evolution laws in different regions were revealed. High-cycle fatigue tests were then conducted on both uncorroded and corroded specimens to evaluate the impact of corrosion damage on fatigue performance. Scanning electron microscopy （SEM） was employed to observe fracture morphologies and elucidate the fatigue behavior characteristics of the clad steel joints. The results indicated that the corrosion process exhibited distinct stages： the mass loss rate increased rapidly during the rust layer formation period but decreased to 51.4% of the initial rate upon entering the stable period. The corrosion resistance of the joints showed heterogeneity， with the stainless steel cladding and weld zones performing optimally， while the transition weld and the heat-affected zone （HAZ） of the weathering steel were identified as corrosion-sensitive areas. Corrosion damage significantly degraded the fatigue performance and altered the failure modes. After 45 days of pre-corrosion， the average fatigue life of the joints decreased by 24.9%. The fracture location shifted from the cladding weld toe to the weld center and transition weld interface， accompanied by the initiation of multiple crack sources and an increase in the number of secondary cracks.