Corrosion Resistance of 9% Cr Oxide Dispersion-Strengthened Steel in Different Electrolytic Media

Abstract

The corrosion resistance and passive film compositions of 9% Cr oxide dispersion-strengthened steel in different acidified and chloride media was evaluated. The results presented below show that with increasing concentrations of 1 M to 11.5 M nitric acid (HNO3), the open-circuit potential reveals a more noble potential, while in chloride-containing media, a less noble potential was observed. The potentiodynamic polarization plots exhibited higher breakdown/transpassive potentials in acidic media with 0.5 M sulfuric acid (H2SO4) and 1 M to 11.5 M HNO3, and there was a shift in the corrosion potential toward the transpassive region as the HNO3 concentration increased from 1 M to 11.5 M. However, no intergranular corrosion attack was observed at the HNO3 concentrations studied. In acidic-chloride media (0.5 M H2SO4 with 0.1 M and 0.5 M sodium chloride [NaCl]) and in chloride only media (0.1 M NaCl and 0.5 M NaCl) poor pitting corrosion resistance was attributable to the microstructural inhomogeneity and inclusions in the steel. The x-ray photoelectron spectroscopy analysis indicated that the passive film has iron(III) oxide (Fe2O3) and chromium(III) oxide (Cr2O3), along with yttrium oxide (Y2O3). The scanning electron microscopy (SEM) examinations showed that the pits on the specimen were hemispherical and formed lace-like patterns. The corrosion properties affected by the dispersed oxide are also discussed in the paper.