Role of imposed potential in expanding the regime of strain rates for caustic cracking

Anodic polarization and caustic cracking tests were carried out on a mild steel in a 20% NaOH caustic solution at 120 C, with and without prior electrochemical conditioning and imposed electrochemical potential. The results presented here suggest that the anodic polarization behavior of the mild steel specimens that were not subjected to prior conditioning is different from those subjected to prior cathodic conditioning. This difference in anodic polarization has implications on caustic cracking susceptibility of mild steel. Imposed potential slow strain rate (SSR) testing was used to study caustic cracking behavior of specimens with and without prior electrochemical conditioning and imposed electrochemical potential during SSR testing. Specimens tested with prior conditioning as well as imposed electrochemical potential showed extended range of strain rates where caustic cracking is observed. This has been related to the quasi-passivity and the presence of activated iron on the surface of test specimens as a result of prior conditioning. (C) 2007 The Electrochemical Society.