Effect of Ni on Pit Depth of 21Cr Ferritic Stainless Steel under the Atmospheric Environment

Abstract

The objective of this study was to clarify effect of Ni on pit depth of 21Cr ferritic stainless steel under the atmospheric environment. The atmospheric exposure test was conducted for 1, 3, 6, 12 and 18 months. After the atmospheric exposure, the depth of each pit was measured by a laser microscope. As a result, the estimated maximum pit depth became shallower by 1.5 mass% Ni addition. The pitting potential measurement test, the anodic polarization measurement test and the corrosion potential measurement test were also conducted. Ni did not have effect on the pitting potential. Ni not only reduced active dissolution but also facilitated repassivation. These electrochemical factors made pit depth shallower.