Underwater wet welding of EH40 steel was performed at 3 m depth using manual metal arc welding. Characterization methods were optical microscopy, microhardness, SEM, EDS, XRD, and electrochemical analyses. The weld metal (WM) consisted of polygonal ferrite and pearlite, with an average grain size of approximately 7.9 μm, while the HAZ contained coarse ferrite/low-carbon martensite and fine ferrite/pearlite. Electrochemical tests showed corrosion rates reached a maximum at 360 h and decreased by 840 h due to protective γ-FeOOH formation. Corrosion resistance followed the order BM > HAZ > WM. Between 360–840 h, pit growth slowed, and product film became denser. Stress corrosion sensitivity wasthe highest in the HAZ, attributed to hydrogen embrittlement and residual stress effects.
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