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J. Ocean Eng. Technol. 2008;22(3):82-88.    

An Electrochemical Study on Corrosion Property of Repair Welding Part for Exhaust Valve
Moon Kyung-Man,Lee Kyu-Hwan,Cho Hwang-Rae,Lee Myung-Hoon,Kim Yun-Hae,Kim Jin-Gyeong
Dept. of Mechanical and Materials Engineering Korea Maritime Univ.,Education and Research Division Korea Institute of Maritime and Fisheries Technology,Dept. of Mechanical and Materials Engineering Korea Maritime Univ.,Dept. of Marine System Engineerin
배기밸브 보수 용접부의 부식 특성에 관한 전기화학적 연구
문경만,이규환,조황래,이명훈,김윤해,김진경
한국해양대학교 공과대학 기계소재공학부,한국해양수산연수원 교육연구,한국해양대학교 공과대학 기계소재공학부,한국해양대학교 해사대학 기관시스템공학부,한국해양대학교 공과대학 기계소재공학부,한국해양수산연수원 교육연구
© 2008 The Korean Society of Ocean Engineers     Open access / Under a Creative Commons License
Keywords: Repair weldment, Weld metal, Plasma welding, Corrosion potential, Corrosion resistance
핵심용어: 보수용접, 용접금속, 프라즈마용접, 부식전위, 내식성
Abstract
The diesel engine of the merchant ship has been aperated in severe environments more and more, because the temperature of the exhaust gas of a combustion chamber is getting higher and higher with increasing use of heavy oil of law quality, due to the significant increase in the price of oil in recent some years. As a result, the degree of wear and corrosion between exhaust valve and seat ring is more serious compared to other engine parts. Thus the repair welding of exhaust valve and seat ring is a unique method to prolong the life of the exhaust valve, from an economical point of view. In this study, the corrosion property of both weld metal and base metal was investigated using electrochemical methods such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram, and polarization resistance in 5% H2SO4 solution. The test specimen was a part of an exhaust valve stem being welded as the base metal, using various welding methods. In all cases, the corrosion resistance as well as hardness of the weld metal zone was superior to the base metal. In particular, plasma welding showed relatively good properties for both corrosion resistance and hardness, compared to other welding methods. In the case of DC SMAW (Shielded metal arc welding), corrosion resistance of the weld metal zone was better than that of the base metal, although its hardness was almost same as the base metal.


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