• 한국결정성장학회지
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• 제28권2호
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• pp.80-84
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• 2018

AZ31과 AZ91 Mg 합금을 Na-P 및 Na-Si 전해질을 사용하여 전해질의 농도, 인가전압, 처리시간에 따라 여러가지 조건에서 PEO 처리하여 5%의 농도를 갖는 염수분무법으로 내부식성 연구를 하였다. 일반적으로 산화피막 코팅 두께가 증가하면 내부식성이 증가하였다. 코팅두께보다 산화피막 표면의 기공크기가 커지면 장기 내부식성은 나빠지는 경향을 보인다. 산화피막의 전체적인 산화물 결정상이 증가할수록, 또 MgO 결정상 대신 $Mg_2SiO_4$ 상과 같은 다른 결정상이 증가할수록 내부식성이 월등히 증가하는 것을 알 수 있었다.

• Corrosion Science and Technology
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• 제16권6호
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• pp.285-293
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• 2017

The effects of sulfate reducing bacteria (SRB) on the corrosion and scaling of the Q235 carbon steel has been investigated in the simulated sewage water and oil field gathering pipelines production water, using scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDS), and three-dimensional stereoscopic microscope. Results indicated that the concentration of SRB reached the maximum value on the ninth day in simulated sewage water with a large amount of scaling on the surface of specimen. In oil field gathering pipelines, a large amount of scaling and mineralization of mineral salts and thick deposition of extracellular polymeric substance (EPS) layers were also observed on the surface of specimen. The thickness of biofilm was about $245{\mu}m$ within 30 days. After adding microbicides, the thickness of corrosion products film was only up to $48-106{\mu}m$ within 30 days, suggesting that SRB could induce biomineralization. Under-deposit corrosion morphology was uniform in the absence of microbicides while local corrosion was observed in the presence of microbicides.

• Corrosion Science and Technology
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• 제10권2호
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• pp.52-59
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• 2011

Corrosion of metallic materials occurs by the reaction with corrosive environment such as atmosphere, marine, soil, urban, high temperature etc. In general, reduction of thickness and cracking and degradation are resulted from corrosion. Corrosion in all industrial facilities and infrastructure causes large economic losses as well as a large number of accidents. Economic loss by corrosion has been reported to be nearly 1-6% of GNP or GDP. In order to reduce corrosion damage of industrial facilities, corrosion map as well as a systematic investigation of the loss of corrosion in each industrial sector is needed. The Corrosion Science Society of Korea in collaboration with 15 universities and institutes has started to survey on the cost of corrosion and corrosion map of Korea since 2005. This work presents the results of the survey on cost of corrosion by Uhlig, Hoar, and input-output methods, and the evaluation of atmospheric corrosion rate of carbon steel, weathering steel, galvanized steel, copper, and aluminum in Korea. The total corrosion cost was estimated in terms of the percentage of the GDP of industry sectors and the total GDP of Korea. According to the result of Input/output method, corrosion cost of Korea was calculated as 2.9% to GDP (2005). Time of wetness was shown to be categories 3 to 4 in all exposure areas. A definite seasonal difference was observed in Korea. In summer and fall, time of wetness was higher than in other seasons. Because of short exposure period (12 months), significant corrosion trends depending upon materials and exposure corrosion environments were not revealed even though increased mass loss and decreased corrosion rate by exposure time.

• 보존과학연구
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• 통권15호
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• pp.52-58
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• 1994

To protect corrosion of bronze roofing tile for Choson Royal Historic Museum, lead coating on tile was performed by electroplating method with thickness of $35\mum$. Lead coated tile samples were inverstigated what corrosion products were formed with color changes on them by testing Accelerated Weathering. No sulfides were formed on samples contacting with 300ppm sulfur dioxide and any color changes were not found. In Accelerated Weathering test, White hydrocerussite, basic lead carbonate($2PbCO_3Pb(OH)_2$) having protective structure made of compact adhering crystals.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.141-148
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• 2002

Repair were made for front pillar, center pillar and side-step panel for lightweight vehicles with head-on and 40% off-set collision of 15 km/h in a RCAR standard. The salt dilution was sprayed and the compression tests were performed for vehicles with and without anti-corrosional treatment after repair. After 764 hours of salt-dilt sprayed test without using anti-corrosion, the mean penetration depth fur corrosion was shown to be 58% of the thickness. The resulyed decrease in bending stiffness by 10∼20% can cause reduction of the residual life and crash-absorption capability for damaged vehicles. The corrosoin safety tests showed that the anti-corrosional treatment should be made to improve the safety characteristics for a or damaged car.

• Steel and Composite Structures
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• 제10권6호
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• pp.475-487
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• 2010

Most of steel structures in various industries are subjected to corrosion due to environmental exposure. Corrosion damage is a serious problem for these structures which may reduce their carrying capacity. These aging structures require maintenance and in many cases, replacement. The goal of this research is to consider the effects of corrosion by developing a model that estimates corrosion loss as a function of exposure time. The model is formulated based on average measured thickness data collected from three severely corroded I-beams (nearly 30 years old). Since corrosion is a time-dependent parameter. Analyses were performed to calculate the lateral buckling capacity of steel beam in terms of exposure time. Minimum curves have been developed for assessment of the remaining lateral buckling capacity of ordinary I-beams based on the loss of thicknesses in terms of exposure time. These minimum curves can be used by practicing engineers for better estimates on the service life of corrosion damaged steel beams.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.693-698
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• 2003

Corrosion of reinforcement and deterioration of concrete short the lifetime of reinforced concrete structure and affect the safety of the structure. In particular, the corrosion of reinforcement causing the inner pressure of the interface between the concrete and reinforcement is known to significantly contribute to the premature deterioration of concrete structure. Several attempts have been made to predict the cracking time of the concrete structure. However, problems such as the lack of reproducibility of concrete tests and non-uniformity of materials have hampered thess kinds of studies. Thus, the mechanism of the concrete cracking due to reinforcement corrosion is in the way. This studymeasured the mechanical properties of corrosion products using the nano-indentation test method. Likewise, the critical thickness of corrosion products for the cracking of concrete cover was investigated using the finite element and experimental methods.

• Journal of Advanced Marine Engineering and Technology
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• 제39권8호
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• pp.828-832
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• 2015

This study is conducted for the evaluation of corrosion and lifetime prediction of fire extinguishing pipelines in residential buildings. The fire extinguishing pipeline is made of carbon steel. Twenty-four samples were selected among all the fire extinguishing pipelines in a building; the selection was based on specimenspositions, pipeline diameters, and pipeline thickness. Analysis was conducted by using the results of visual inspection, electrochemical potentiodynamic anodic polarization test, pitting depth measurements, and extreme value statistics with the Gumbel distribution. The maximum pitting depth and remaining life were statistically predicted using extreme value statistics. During visual inspection, pitting corrosion was observed in several samples. In addition, extreme value statistics demonstrated that there were several pipelines that were very sensitive to pitting corrosion. However, the pitting corrosion was not critical in all the pipelines; thus, it was necessary to change only those pipelines that were severely corroded.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.228-233
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• 2004

The length of city gas pipeline is increasing with expansion of natural gas transmission rapidly. A lot of the expense was paid for repair and maintenance with increasing of pipeline length and the cost of repair and maintenance by the corrosion was the highest. It is necessary to evaluate integrity in case of thickness reduction by corrosion. There are a lot of assessment criteria for corrosion defect in foreign countries but they are not suitable for application in the country directly. In this work, we performed the burst test and the finite element analysis for city gas pipeline, KS D3507 and KS D3631 for city gas transmission, and developed the assessment method of corrosion defect, which is suitable for domestic condition.

• 한국재료학회지
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• 제29권5호
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• pp.288-296
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• 2019

The passivation of AZ91D Mg alloys through plasma anodization depends on several process parameters, such as power mode and electrolyte composition. In this work, we study the dependence of the thickness, composition, pore formation, surface roughness, and corrosion resistance of formed films on the electrolyte temperature at which anodization is performed. The higher the electrolyte temperature, the lower is the surface roughness, the smaller is the oxide thickness, and the better is the corrosion resistance. More specifically, as the electrolyte temperature increases from 10 to $50^{\circ}C$, the surface roughness (Ra) decreases from 0.7 to $0.15{\mu}m$ and the corrosion resistance increases from 3.5 to 9 in terms of rating number in a salt spray test. The temperature increase from 10 to $50^{\circ}C$ also causes an increase in magnesium content in the film from 25 to 63 wt% and a decrease in oxygen from 66 to 21 wt%, indicating dehydration of the film.