Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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Selective Corrosion of Socket Welds of Stainless Steel Pipes Under Seawater Atmosphere

해수분위기에서 스테인리스강 배관 소켓 용접부의 선택적 부식

  • Boo, Myung-Hwan (Central Research Institute, Korea Hydro & Nuclear Power Co., Ltd) ;
  • Lee, Jang-Wook (Central Research Institute, Korea Hydro & Nuclear Power Co., Ltd) ;
  • Lee, Jong-Hoon (Central Research Institute, Korea Hydro & Nuclear Power Co., Ltd)
  • 부명환 (한국수력원자력(주) 중앙연구원) ;
  • 이장욱 (한국수력원자력(주) 중앙연구원) ;
  • 이종훈 (한국수력원자력(주) 중앙연구원)
  • Received : 2020.06.30
  • Accepted : 2020.08.25
  • Published : 2020.08.31
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Abstract

Stainless steel has excellent corrosion resistance. The drawback is that pitting occurs easily due to the concentration of chloride. In addition, corrosion of socket weld, which is structurally and chemically weaker than the other components of the pipe, occurs rapidly. Since these two phenomena overlap, pinhole leakage occurs frequently in the seawater pipe socket welds made of stainless steel at the power plants. To analyze this specific corrosion, a metallurgical analysis of the stainless steel socket welds, where the actual corrosion occurred during the power plant operation, was performed. The micro-structure and chemical composition of each socket weld were analyzed. In addition, selective corrosion of the specific micro-structure in a mixed dendrite structure comprising γ-austenite (gamma-phase iron) and δ-ferrite (iron at high temperature) was investigated based on the characteristic micro-morphology and chemical composition of the corroded area. Finally, the different corrosion stages and characteristics of socket weld corrosion are summarized.

Keywords

References

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