The influence of temperature and the role of chromium in the passive layer in relation to pitting corrosion of 316 stainless steel in NaCl solution

✍ Scribed by C. Pallotta; N. De Cristofano; R.C. Salvarezza; A.J. Arvia

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 532 KB
• Volume: 31
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(86)80146-3

✦ Synopsis

The electrochemical behaviour of 316 stainless steel was studied in nearly neutral electrolytes containing NaCl in the -3 to 50°C temperature range, using potentiostatic and potentiodynamic techniques. Special attention was paid to both the current fluctuations previous to the irreversible breakdown of the passive film and to the breakdown potential. No pitting was observed at temperature lower than 0°C. In the &lS"C range the breakdown potential shifts slightly in the negative direction. Between 15 and 25°C a remarkable decrease in the breakdown potential was observed whereas in the 2550°C range it remained practically constant. The temperature dependence of the breakdown potential correlates closely with the temperature dependence of the Cr(lI1) to soluble Cr(V1) electrooxidation current. This suggests that the depletion of Cr(III) and surrounding water with increasing temperature decreases the capability of self-repair of the passive film. Conversely, the increase in temperature produces a thicker and more crystalline passive film which becomes more resistant to breakdown. As this effect is counterbalanced by the depletion of Cr(Il1) in the passive layer the breakdown potential in the 25-50°C range remains practically constant.