ステンレス鋼における化合物依存型粒界腐食機構

抄録

Following the first paper on the study of the composition dependent intergranular corrosion (IGC) mechanism of stainless steels (SS), the compound dependent IGC mechanism has been studied in this paper. In this mechanism, IGC is induced by the dissolution of grain boundary (GB) precipitates of themselves.
It was confirmed that the IGC mechanism played an important role mainly in the transpassive state corrosion potential region above about 1.2V(SHE), where neither the Cr depleted zone nor the segregation of P at GB induced IGC. The film-like and amorphous Ni-P compound, [Ni (Fe, Cr)]₃P₂ was found to precipitate at GB in Type 304 SS and to cause very thin but very deep IGC. Also, intermetallic compounds of Laves and χ phases were identified to precipitate at GB and to induce severe IGC due to the dissolution of themselves in Type 316 SS.