Electrochemical Corrosion Resistance of 304 Stainless Steel after Sensitization

The sensitization degree of 304 stainless steel after heating at 600 ℃ for different times was evaluated by electrochemical potentiodynamic reactivation. The electrochemical corrosion behavior of tested steel with different sensitization degrees in 4vol% acetic acid solution, 5wt% NaCl solution and the two solution mixture with volume ratio of 1∶1, respectively, and the influence of immersion time and solution temperature on the electrochemical corrosion resistance of tested steel with the same degree of sensitization were studied. The results show that with the increase of holding time, the reactivation current of tested steel increased, and the sensitization degree increased. With the increase of sensitization degree, the self-corrosion potential of tested steel in NaCl solution and NaCl/acetic acid mixed solution shifted negatively, and the corrosion resistance decreased; the self-corrosion potential in acetic acid solution shifted positively, and the corrosion resistance was improved. With the extension of immersion time, the self-corrosion potential of tested steel in NaCl solution shifted negatively, and the corrosion resistance decreased; the self-corrosion potential in acetic acid solution shifted positively, and the corrosion resistance was improved; the self-corrosion potential in NaCl/acetic acid mixed solution changed little, and the corrosion resistance was basically unchanged. With the increase of solution temperature, the self-corrosion current densities of tested steel in different solutions all increased.