• 제목/요약/키워드: Local corrosion

검색결과 245건 처리시간 0.029초

지점부 부재의 부식손상에 따른 강거더 단부 지압강도 평가 (Evaluation on Bearing Capacity of End Girder Member with Local Corrosion)

  • 안진희;이원홍;김인태;정영수
    • 한국구조물진단유지관리공학회 논문집
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    • 제21권5호
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    • pp.74-82
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    • 2017
  • 강교량은 유지관리가 충분히 이루어지지 않거나, 해안 과 같이 가설위치의 환경이 고온 다습한 경우 단면에 국부적인 부식손상이 발생할 수 있다. 특히 강거더 교량 의 지점부에서는 교대부와 강거더 단부의 공간이 협소하여 상대적으로 습도가 높고 신축이음부로부터의 강우 및 동결 방지제가 누수되어 침전물을 습윤상태로 유지하게 되므로, 복부판과 지점부 보강재에 집중적으로 부식이 발생되고 있으므로 이로인한 구조성능 변화를 확인하여야 한다. 따라서 본 연구에서는 실제 발생할 수 있는 강거더 단부 복부판과 보강재의 국부부식손상을 모사한 강재 실험체를 제작하고 이에 대한 단부 지압강도 변화를 실험적으로 평가하였다. 실험결과, 국부적 부식손상은 강거더 단부의 지압강도에 영향을 주며, 특히 수직 보강재에 의한 영향이 크게 나타남을 확인하였다.

Corrosion Characteristics of Welding Zones Welded with 1.25Cr-0.5 Mo Filler Metal to Forged Steel for Piston Crown Material

  • Jeong, Jae-Hyun;Lee, Sung-Yul;Lee, Myeong-Hoon;Baek, Tae-Sil;Moon, Kyung-Man
    • Corrosion Science and Technology
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    • 제14권2호
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    • pp.54-58
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    • 2015
  • A heavy oil of low quality has been mainly used in the diesel engine of the merchant ship as the oil price has been significantly jumped for several years. Thus, a combustion chamber of the engine has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of the combustion chamber has been getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the engine parts such as exhaust valve, piston crown and cylinder head surrounded with combustion chamber are more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these engine parts is very important to prolong their lifetime in a economical point of view. In this study, 1.25Cr-0.5Mo filler metal was welded with SMAW method in the forged steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected and base metal zones were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% $H_2SO_4$ solution. The weld metal and base metal zones exhibited the highest and lowest values of hardness respectively. And, the corrosion resistance of the heat affected and weld metal zones was also increased than that of the base metal zone. Furthermore, it appeared that the corrosive products with red color and local corrosion like as a pitting corrosion were more frequently observed on the surface of the base metal zone compared to the heat affected and weld metal zones. Consequently, it is suggested that the mechanical and corrosion characteristics of the piston crown can be predominantly improved by repair welding method using the 1.25Cr-0.5Mo electrode.

잠재성 특이산성토중 강관말뚝의 부식 (Steel Pile Corrosion in Potential Acid Sulfate Soil)

  • 이승헌;박미현;윤경섭
    • 한국농공학회:학술대회논문집
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    • 한국농공학회 2003년도 학술발표논문집
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    • pp.559-562
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    • 2003
  • The results and discussions of surveyed case site at constructed steel pile in potential acid sulfate soil were as follows. Topography at surveyed site was local alluvial valley and that site soils was classified as BanGog and YuGye series as detailed soil surveyed results in RDA and soil texture was Clay/Clay Loam. Soils pH was neutral, which was average 7.5 but much decreased to average 4.2 after $H_2O_2$ treatment. Organic matter and sulfate ions contents were very rich. The corrosion was severe at ground water fluctuation depth. Deposits colored black were attached to steel pile surface, which because of violent reaction in treatment HCI solution, were guessed as corrosion products (FeS) reduced by sulfate reducing bacteria(SRB). Consequently, main cause was thought microbiologically induced corrosion at this site where there is ground water fluctuation occurring oxidation and reduction reactions in turn and the soil is potential acid sulfate soil.

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마이크로 드로플릿 셀 기법을 이용한 예민화 된 304 스테인리스강의 미세전기화학 특성 (Micro-electrochemical Characteristics of Sensitized 304 Stainless steel Using Micro-droplet cell Techniques)

  • 김규섭;이재봉
    • Corrosion Science and Technology
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    • 제9권6호
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    • pp.300-309
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    • 2010
  • The influences of sensitization on localized corrosion resistance of 304 stainless steel, were investigated, using micro-dropletcell techniques. Micro-droplet cell allows one to align the micro-electrode to the desired spot of the working electrode and measure directly local current with the potentiodynamic polarization, linear polarization and a.c. impedance. Micro-electrochemical tests were carried out inside of the grain and on grain boundaries separately. It was found that sensitization decreased the pitting potential, increasing corrosion current density around grain boundaries. Galvanic current density was also measured between grain and grain boundaries.

Micro-droplet cell을 이용한 Fe-17Cr 합금의 공식 발생에 대한 연구 (A Study on the Initiation of Pitting Corrosion of Fe-17Cr Alloy Using Micro-Droplet Cell Technique)

  • 김재중;이재봉
    • 대한금속재료학회지
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    • 제46권12호
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    • pp.809-816
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    • 2008
  • The influences of various parameters such as inclusions, surface roughness, exposed areas and chloride ion concentrations on the initiation of pitting of Fe-17Cr alloy were investigated, using micro-droplet cell technique. Micro-droplet cell allows one to align the micro-electrode to the desired spot of the working electrode and measure directly local currents with the potentiodynamic polarization. Micro electrochemical tests were carried out at the inclusions after EDX analysis of inclusion. EDX analysis identified inclusions as Cr-oxides. It was found that some active inclusions among Cr-oxide inclusions acted as initiation sites for pitting corrosion. In addition, the rougher surface and the denser chloride ion concentration offered easier pit initiation sites, causing the more susceptible to pitting corrosion.

국부 부식을 가지는 심해저 파이프라인의 구조응답에 대한 전산 해석적 연구 (Computational Analysis of Structural Behavior of Subsea Pipelines with Local Corrosion)

  • 최광호;이치승;유동만;구본용;송준규;이제명
    • 한국해양공학회지
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    • 제29권1호
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    • pp.100-110
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    • 2015
  • To meet the increasing demand for energy around the world, offshore and subsea energy development is constantly being conducted. This trend is accompanied by an increasing demand for pipeline installation, which brings numerous problems, including those related to accessibility, high pressure, and corrosion. Among these, corrosion is a primary factor in pipeline fractures, and can cause severe environmental and industrial damage. Hence, accurate corrosion assessment for corroded pipelines is very important. For this reason, the present study investigated the mechanical behavior of an idealized corroded subsea pipeline with an internal/external pressure load using the commercial FEA code ABAQUS. Then, the analysis result was compared with corrosion assessment codes such as ASME B31G, DNV RP F101, ABS. Finally, a fitness-for-service assessment was conducted.

Al-황동의 분극특성에 미치는 응력의 영향 (Effect of Stress on the Polarization Characteristic of Al-brass)

  • 임우조;정해규;심경태
    • 한국안전학회지
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    • 제19권2호
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    • pp.1-5
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    • 2004
  • Al-brass is the raw material of mnufacturing tubes for heat exchanger of vessel where seawater is used to coolant because it has high level of heat coductivity and excellent mechanical properties and high level of corrosion resistance due to cuprous oxide($Cu_2O$) layer against seawater. However, damage of Al-brass tubes for heat exchanger of vessel is reported that local corrosion such as stress corrosion cracking occurred by synergism effect between mechanical factor and corrosion environment. In this study, to investigate on the effect of stress on the polarization characteristics of Al-brass. At the stress of 0% and 95% yield strength by constant displacement tester, in 3.5% NaCl + 0.1% $NH_4OH$ solution, the polarization tests were carried out. And thus open circuit potential, corrosion current density, anodic polarization, cyclic polarization and dezincification behavior of Al-brass are investigated.

Relation between total degradation of steel concrete bond and degree of corrosion of RC beams experimental and computational studies

  • Maurel, Olivier;Dekoster, Mickael;Buyle-Bodin, Francois
    • Computers and Concrete
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    • 제2권1호
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    • pp.1-18
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    • 2005
  • This paper presents a study on the effects of localized steel-concrete bond degradation on the flexural behaviour of RC beams. A finite element analysis is undertaken to complete the experimental analysis. The first part deals with an experimental study on beams where bond was removed by using plastic tube at different locations and for various lengths. The flexural behaviour was studied at global scale (load-deflection) and local scale (moment-curvature). The second part, a numerical study using a simplified special finite element (rust element) modelling the rust layer occurring between reinforcement and concrete with corrosion was conducted in order to find the relation between the degree of corrosion and the degradation of the steel-concrete bond. The computed value of the corrosion degree corresponding to the total degradation of bond has been used in a second time to model the tests, in order to evaluate the influence of the loss of bond, the steel cross section reduction, and the combination of both. The results enable to evaluate the influence of the different corrosion effects on the flexural behaviour, according to the length and the location of the corroded zone.

Numerical Simulation of Interactions between Corrosion Pits on Stainless Steel under Loading Conditions

  • Wang, Haitao;Han, En-Hou
    • Corrosion Science and Technology
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    • 제16권2호
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    • pp.64-68
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    • 2017
  • The interactions between corrosion pits on stainless steel under loading conditions are studied by using a cellular automata model coupled with finite element method at a mesoscopic scale. The cellular automata model focuses on a metal/film/electrolyte system, including anodic dissolution, passivation, diffusion of hydrogen ions and salt film hydrolysis. The Chopard block algorithm is used to improve the diffusion simulation efficiency. The finite element method is used to calculate the stress concentration on the pit surface during pit growth, and the effect of local stress and strain on anodic current is obtained by using the Gutman model, which is used as the boundary conditions of the cellular automata model. The transient current characteristics of the interactions between corrosion pits under different simulation factors including the breakdown of the passive film at the pit mouth and the diffusion of hydrogen ions are analyzed. The analysis of the pit stability product shows that the simulation results are close to the experimental conclusions.

감육을 가지는 배관 용접부의 파괴거동 (Fracture Behavior of Welded Pipes with Local Wall Thinning)

  • 안석환;남기우;정정환;김용운
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 춘계학술대회
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    • pp.90-95
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    • 2003
  • Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. In pipes of energy plants, sometimes, the local wall thinning may result from severe erosion-corrosion (E/C) damage. However, the effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. In this paper, the monotonic bending tests were performed of full-scale welded and unwelded carbon steel pipes with local wall thinning. A monotonic bending load was applied to straight pipe specimens by four-point loading at ambient temperature without internal pressure. The observed failure modes were divided into four types; ovalization, crack initiation/growth after ovalization, local buckling and crack initiation/growth after local buckling. Also, the strengths of welded and unwelded piping system with local wall thinning were evaluated.

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