Effect of Alloying Elements on the Rate of Growth of Individual Pits on Stainless Steels

✍ Scribed by Marinovich, Y. ;Fukutsuka, T. ;Matsuo, Y. ;Sugie, Y.

• Publisher: Curtin University of Technology
• Year: 2008
• Tongue: English
• Weight: 699 KB
• Volume: 11
• Category: Article
• ISSN: 0969-1855
• DOI: 10.1002/apj.5500110608

✦ Synopsis

Abstract

Potentiodynamic polarization curves of five different commercially available stainless steels (SS) were measured in air‐saturated 0.5 M NaCl (25d̀C, pH = 5.2). This data gave useful information on the corrosion behavior of the alloys in this system. It was found that the potential at which pitting begins becomes more positive with increasing Cr and Ni content. A strong relationship between the magnitude of the cathodic current density and the electrode surface area was also observed, and a reason for this observation was suggested. Potentiostatic pitting experiments were performed in order to determine the effect of Cr, Ni, Ti and Mo concentrations on the growth rate of a single pit. However, quantitative data was not obtained since it proved difficult to form a single pit on the SS microelectrode. Instead, many pits formed over the surface thus making quantitative analysis of the current transients impossible. The reason for this phenomenon is still unclear. With 316 SS, both ideal hemispherical and irregularly shaped pits were observed to occur together. From Electron Probe Micro Analysis (EPMA) mapping it was shown that sulfide inclusions were probably not responsible for producing pit nucleation sites on 316 SS.