Anodic Dissolution Behavior of Crack Tip Under Synergistic Effect of Strain and Polarization
During the service life of metal materials,the tips of their surface cracks undergo local plastic deformation preferentially under the influence of stress.Additionally,the combined effect of polarization leads to significant differences in both corrosion behavior and corrosion rate between the crack tip and other zones.This research employed a custom-designed in-situ loading platform,integrated with scanning vibrating Electrode technology(SVET)and an electrochemical workstation,to thoroughly investigate the corrosion behavior at the tips of 316L stainless steel cracks in acidic NaCl solutions.Key conclusions are drawn as follows:The crack tip is a stress concentration zone where increased strain leads to the rupture of the passive film at the crack tip and rapid localized anodic dissolution of the metal.When the metal is at open-circuit potential or at a low anodic polarization potential,the newly exposed metal surface at the crack tip can rapidly passivate,causing the total current to briefly rise and then swiftly drop.At higher anodic polarization potentials,even if within the passivation range of 316L stainless steel,the newly exposed metal surface can't repassivate,resulting in sustained anodic dissolution at localized crack tips.Above the pitting potential,not only do pitting corrosion occur on the 316L surface,but the newly exposed metal surfaces due to strain also fail to repassivate,making both the crack tips and pitting sites continual zones of anodic dissolution on the sample surface.
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