Microelectrochemical aspects of interstitial carbon in type 304 stainless steel: Improving pitting resistance at MnS inclusion

Aya Chiba, Shuhei Shibukawa, Izumi Muto, Takashi Doi, Kaori Kawano, Yu Sugawara, Nobuyoshi Hara

研究成果: Article査読

26 被引用数 (Scopus)

抄録

Type 304 stainless steel was subjected to low-temperature carburizing treatment to add excess interstitial carbon to its surface. The average carbon concentration in the carburized layer was ca. 2.6 mass%, and the lattice parameter was expanded by ca. 2.5% without any carbide precipitation. No pitting was initiated on the carburized stainless steel in 0.1 M NaCl. Microscopic polarization measurements of a small area with a MnS inclusion were performed in NaCl and Na2SO4 solutions to clarify the mechanism of the improved resistance against pitting corrosion. The anodic polarization in 0.1 M NaCl and 0.1 M Na2SO4 demonstrated that the carburizing treatment has little or no effect on the electrochemical dissolution behavior of the MnS inclusions. However, from the anodic polarization of the steel in the solution that simulates the vicinity of the dissolved MnS inclusions in chloride-containing environments, it was clarified that the carburizing treatment inhibits the active dissolution rate of the steel matrix to about one hundredth. It would appear that interstitial carbon inhibits the dissolution rate of the steel, resulting in a reduction in the dissolution depth of the trenches at the MnS/steel boundaries. It is likely that the carburization resulted in a suppression of both the acidification due to the hydrolysis reaction of Cr3+ and the potential decrease due to IR-drop in the trenches to the extent that the corrosivity inside the trenches is insufficient for the localized transition from the passive to active state. Therefore, pit initiation does not occur at the MnS inclusions on the carburized stainless steel in chloride-containing environments.

本文言語English
ページ(範囲)C270-C278
ジャーナルJournal of the Electrochemical Society
162
6
DOI
出版ステータスPublished - 2015

ASJC Scopus subject areas

  • 電子材料、光学材料、および磁性材料
  • 再生可能エネルギー、持続可能性、環境
  • 表面、皮膜および薄膜
  • 電気化学
  • 材料化学

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