2006 Volume 55 Issue 2 Pages 70-74
Surface analysis through Auger Electron Spectroscopy was conducted on Type 316 L stainless steel (SS) and two kinds of N-alloyed austenitic SS. One was 16Cr-14Ni-2Mo-0.17N SS, which contained 16%Cr, 14%Ni, 2%Mo and 0.17%N. The other was 18Cr-2Mo-1N SS, which contained 18%Cr, 2%Mo and 1%N. Cr on the surface of 16Cr-14Ni-2Mo-0.17N SS and 18Cr-2Mo-1N SS was concentrated after active dissolution treatments in 0.5 mol · dm-3 H2SO4 containing 0.5 mol · dm-3 NaCl. However, in both cases of 16Cr-14Ni-2Mo-0.17N SS and 18Cr-2Mo-1N SS, the concentration of Cr was not higher than that of Type 316L SS. Crevice corrosion tests and repassivation tests were conducted on Type 316L SS and 18Cr-2Mo-1N SS. The lowest value of potentials, at which crevice corrosion was initiated and propagated in synthetic seawater at 35°C, for 18Cr-2Mo-1N SS was still nobler than that for Type 316L SS. Repassivation potentials for crevice corrosion did not depend on the crevice corrosion depth in the case of Type 316L SS. On the other hand, the repassivation potential for 18Cr-2Mo-1N SS decreased with increasing crevice corrosion depth and came equivalent to that for Type 316L SS at a crevice corrosion depth of 0.3 mm.