Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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Effect of Lead Concentration on Surface Oxide Formed on Alloy 600 in High Temperature and High Pressure Alkaline Solutions

고온, 고압 알칼리 수용액에서의 Alloy 600 산화막 특성에 미치는 납 농도 영향

  • Kim, Dong-Jin (Nuclear Materials Division, Korea Atomic Energy Research Institute) ;
  • Kim, Hyun Wook (Nuclear Materials Division, Korea Atomic Energy Research Institute) ;
  • Moon, Byung Hak (Nuclear Materials Division, Korea Atomic Energy Research Institute) ;
  • Kim, Hong Pyo (Nuclear Materials Division, Korea Atomic Energy Research Institute) ;
  • Hwang, Seong Sik (Nuclear Materials Division, Korea Atomic Energy Research Institute)
  • 김동진 (한국원자력연구원 원자력재료개발부) ;
  • 김현욱 (한국원자력연구원 원자력재료개발부) ;
  • 문병학 (한국원자력연구원 원자력재료개발부) ;
  • 김홍표 (한국원자력연구원 원자력재료개발부) ;
  • 황성식 (한국원자력연구원 원자력재료개발부)
  • Received : 2012.05.15
  • Accepted : 2012.06.28
  • Published : 2012.06.30
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Abstract

Outer diameter stress corrosion cracking (ODSCC) has occurred for Alloy 600 (Ni 75 wt%, Cr 15 wt%, Fe 10 wt%) as a heat exchanger tube of the steam generator (SG) in nuclear power plants (NPP) during long term operation. Among many causes for SCC, lead (Pb) is known to be one of the most deleterious species in the secondary system. In the present work, the oxide formed on Alloy 600 was characterized as a function of the PbO content in 0.1 M NaOH at $315^{\circ}C$ by using an electrochemical impedance spectroscopy (EIS), a transmission electron microscopy (TEM), equipped with an energy dispersive x-ray spectroscopy (EDS). The oxide property was analyzed in view of SCC susceptibility.

0.1 M NaOH 용액에 PbO첨가양이 증가함에 따라 Alloy 600에 형성되는 산화막의 부동태 피막 특성이 열화되었다. 또한 뚜렷한 2중층 구조의 산화막이 점차 사라지고, 산화막내 존재하는 납의 양이 증가하였다. 산화막 내부 납의 양이 증가함에 따라 산화막 내부 니켈의 결핍이 점차 커졌다. 납에 의해 산화막의 부동태 특성이 약화됨에 따라, 응력부식균열 저항성 또한 급감하였을 것으로 판단된다.

Keywords

References

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