Effect of Applied Potentials on Room Temperature Stress Corrosion Cracking of Austenitic Stainless Steel Weldments

Autogenous welds were made on AISI 316 (UNS S31600) SS sheets, using tungsten inert gas (TIG) welding process. All-weld metal (WM) and base metal (BM) tensile samples were made and tested for stress corrosion cracking (SCC) susceptibility in 5 N H₂SO₄ + 0.5 N NaCl solution at room temperature in two conditions, as welded (WM) and solutionized (BM), and sensitized (both WM and BM). Constant load-type equipment was used to assess the SCC behavior at open-circuit and applied potentials. Failure times for each applied potential under the same level of stress (340 MPa) were noted. Under anodic applied potentials, the time to failure was reduced in comparison to that at the steady-state rest potential (E_R) condition. When cathodic potentials were applied, the time to failure was increased relative to that at E_R. Base metals in the solutionized and sensitized conditions took longer to fail than their weld metals under identical conditions, indicating the harmful effect of ferrite on SCC at all potentials. Weld metals required more cathodic potentials than their base metal counterparts to avoid SCC. The results are substantiated by optical and scanning electron microscopies performed after SCC failure.