オーステナイト系ステンレス鋼のアノード分極挙動に及ぼすアスコルビン酸の影響

抄録

The corrosion behavior of austenitic stainless steels was investigated in solutions of L-ascorbic acid (C₆H₈O₆), which is thought to be a material having a corrosive action on stainless steel, by measuring anodic polarization curves. It was found that C₆H₈O₆ had an aggressively corrosive action on stainless steels. The critical current density for passivation of the specimens increased with increasing C₆H₈O₆ content up to about 10%, but above that level had a tendency to decrease. C₆H₈O₆ tended to accelerate the cathodic reaction, but, for easily corroced specimens such as SUS 303, it mainly accelerated the anodic reaction. The addition of NaCl to C₆H₈O₆ solutions enlarged the active region of the anodic polarization curves of the specimens and pitting potentials had a tendency to become less noble. Further, the passive potential region of those curves become narrow. In the active region, the matrix of the specimens dissolved preferentially at potentials less noble than the passivation potential (anodic current maximun in the active region), while MnS inclusions dissolved preferentially at potentials equal to or more noble than the passivation potential. At potentials more noble than the penetration potential, which corresponded to reincreasing current after passivation, shallow localized corrosion occurred, whereas in the pitting potential region in solutions containing NaCl, pitting began from MnS or MnSe inclusions.