Microbiologically Influenced Corrosion (MIC) occurring in underground buried pipes of API 5L X65 steel was investigated. MIC is a corrosion phenomenon caused by microorganisms in soil; it affects steel materials in wet atmosphere. The microstructure and mechanical properties resulting from MIC were analyzed by OM, SEM/EDS, and mapping. Corrosion of pipe cross section was composed of ① surface film, ② iron oxide, and ③ surface/internal microbial corrosive by-product similar to surface corrosion pattern. The surface film is an area where concentrations of C/O components are on average 65 %/ 16 %; the main components of Fe Oxide were measured and found to be 48Fe-42O. The MIC area is divided into surface and inner areas, where high concentrations of N of 6 %/5 % are detected, respectively, in addition to the C/O component. The high concentration of C/O components observed on pipe surfaces and cross sections is considered to be MIC due to the various bacteria present. It is assumed that this is related to the heat-shrinkable sheet, which is a corrosion-resistant coating layer that becomes the MIC by-product component. The MIC generated on the pipe surface and cross section is inferred to have a high concentration of N components. High concentrations of N components occur frequently on surface and inner regions; these regions were investigated and Na/Mg/Ca basic substances were found to have accumulated as well. Therefore, it is presumed that the corrosion of buried pipes is due to the MIC of the NRB (nitrate reducing bacteria) reaction in the soil.

Abstract
1. 서 론
2. 실험방법
3. 실험결과
    3.1. 초기 및 안정기 부식 형상
    3.2. 배관 표면 부식 성분 분석
    3.3. 배관 단면 부식층 분석
    3.4. 배관 표면 및 단면 부식층 분석
4. 고 찰
5. 결 론
Acknowledgemen
References

• 최병학(강릉원주대학교 신소재금속공학과) | Byung Hak Choe (Dept. of Metal and Materials Engineering, Gangneung-Wonju National Univ., Gangneung 25457, Republic of Korea) Corresponding author
• 한성희(강릉원주대학교 신소재금속공학과) | Sung Hee Han (Dept. of Metal and Materials Engineering, Gangneung-Wonju National Univ., Gangneung 25457, Republic of Korea)
• 김대현(강릉원주대학교 신소재금속공학과) | Dae Hyun Kim (Dept. of Metal and Materials Engineering, Gangneung-Wonju National Univ., Gangneung 25457, Republic of Korea)
• 김우식(한국가스공사 가스연구원) | Woosik Kim (KOGAS Research Institute (R&D Division Korea Gas Corporation), Ansan 15328, Republic of Korea)
• 김철만(한국가스공사 가스연구원) | Cheolman Kim (KOGAS Research Institute (R&D Division Korea Gas Corporation), Ansan 15328, Republic of Korea)
• 최광수(국립과학수사연구원 법공학부 안전과) | Kwang Su Choi (Forensic Safety Division, National Forensic Service, Wonju 26460, Republic of Korea)