• 도시과학
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• 제7권1호
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• pp.23-27
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• 2018

This research was carried out to investigate the corrosion prevention effect in the water distribution system by galvanized zinc-brass pipe which is using potential between brass and zinc. As a result of this study, pH and conductivity of influent were constant in spite of its installation, and it was difficult to estimate the effect of the installation with temporary increased and reduced concentration of Zn and Fe ions, respectively. However, since the corrosion rate of the steel coupon with galvanized zinc-brass pipe was relatively low, it has an effect of inhibiting corrosion.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.133-138
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• 2002

Microbiologically Influenced Corrosion (MIC) was suspected in a corrosion failure of cooling system of stainless piping welded joint, carrying marine water. Marine water which is used for cooling water in a plant was transferred to the laboratory and used for experiment. In the first experiment, weld metal samples were exposed to the test solution for 56 days (marine water and sterilized marine water (control)). Surface condition of experimental coupons was observed using a Scanning Electron Microscope (SEM). In another experiment, free corrosion potential of these material was monitored for 56 days. Pitting corrosion was found in the coupons exposed to marine water. Free corrosion potential ennoblement was found to be significant compared to control. It was suspected that this corrosion case was MIC. In the second experiment, coupons were exposed to diluted nutrient medium containing single culture of microbes isolated from the MIC causing marine water sample used for the first experiment. After exposure test, surface condition of experimental coupon was observed using SEM. Pitting corrosion was found in coupons exposed to some of the isolates. The results indicate that they contribute to the corrosive effect of the SUS316L welds.

• Nuclear Engineering and Technology
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• 제50권5호
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• pp.788-793
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• 2018

High-density spent fuel (SF) storage racks have been installed to increase SF pool capacity. In these SF racks, neutron absorber materials were placed between fuel assemblies allowing the storage of fuel assemblies in close proximity to one another. The purpose of the neutron absorber materials is to preclude neutronic coupling between adjacent fuel assemblies and to maintain the fuel in a subcritical storage condition. METAMIC neutron absorber has been used in high-density storage racks. But, neutron absorber materials can be subject to severe conditions including long-term exposure to gamma radiation and neutron radiation. Recently, some of them have experienced degradation, such as white spots on the surface. Under these conditions, the material must continue to serve its intended function of absorbing neutrons. For the first time in Korea, this article uses a neutron attenuation test to examine the performance of METAMIC surveillance coupons. Also, scanning electron microscope analysis was carried out to verify the white spots that were detected on the surface of METAMIC. In the neutron attenuation test, there was no significant sign of boron loss in most of the METAMIC coupons, but the coupon with white spots had relatively less B-10 content than the others. In the scanning electron microscope analysis, corrosion material was detected in all METAMIC coupons. Especially, it was confirmed that the coupon with white spots contains much more corrosion material than the others.

• 상하수도학회지
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• 제25권2호
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• pp.193-199
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• 2011

A method to improve internal corrosion control efficiency by adding lime and carbon dioxide, which, in turn increases the Langelier Index (LI) for filtered water at a conventional drinking water treatment plant (WTP) was investigated. The SJ WTP (Q=100,000 $m^{3}$/d) has been operating an internal corrosion control system since 2006. The system has achieved stable operation through technical development and trial and error over a period of several years. As a result of the operation, the LI of treated water has increased up to 29% by adjusting pH of filtered water to 7.8 with the addition of lime and carbon dioxide. Coupon tests in the distribution system indicated that the corrosion rate has been delayed by 24% when the internal corrosion method was implemented. The increase of LI by lime and carbon dioxide has been proven to be a practical method for controlling corrosion.

• Corrosion Science and Technology
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• 제14권6호
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• pp.267-272
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• 2015

The performance of three tubular materials (C-90, L-80, and N-80) was evaluated in a synthetic brine inoculated with sulfate-reducing bacteria (SRB) in the absence and presence of biocides. A flow loop was used in the evaluation of the three alloys. Morphological examination of the alloy surfaces after exposure to SRB and after biocide treatment was performed by scanning electron microscopy (SEM) to determine the nature of any localized corrosion. The SE images of the coupon samples showed a marked difference between the biocide-treated and untreated samples. Small pits were observed on the ultrasonically cleaned surfaces of the three alloys after exposure to SRB. The biocide treatment reduced the number of SRB on the surfaces of the alloys. Results indicated that C-90 and L-80 alloys exhibited better MIC resistance than N-80 under the conditions used in this study.

• 상하수도학회지
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• 제20권4호
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• pp.509-518
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• 2006

Although final water of domestic water treatment plants almost contains highly corrosive characteristics, the countermeasures for eliminating internal corrosion of pipeline system have not been conducted yet by controlling water quality in plants. The technologies of internal corrosion control are to control water quality parameters(pH, Alkalinity, and Calcium Hardness etc.) and to use corrosion inhibitor. Under the conditions of domestic water treatment, first of all, the technologies of adjusting water quality parameters has to be considered. Otherwise, The technology of using corrosion inhibitor is favorably thought to be applied with the technology of adjusting water quality parameters in accordance with the result of availability for water treatment process. Since the technology of adjusting water quality parameter influences on other water treatment processes, the guideline of water quality management to be apt for water quality characteristic is required to be estabilished. While the selection of proper chemicals and technologies is dependent upon the raw water characteristics and water treatment process, typically, the technology of $Ca(OH)_2$ & $CO_2$ additions is considered more effective than other technologies in order to adjust pH and Alkalinity, increase $Ca^{2+}$ and form $CaCO_3$ film

• Corrosion Science and Technology
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• 제16권5호
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• pp.227-234
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• 2017

Reference electrodes are generally implemented for the purpose of monitoring the cathodic protection potentials of buried or immersed metallic structures. In the market, many types of reference electrodes are available for this purpose, such as saturated calomel, silver/silver chloride and copper/copper sulfate. These electrodes contain a porous ceramic junction plate situated in the cylindrical body bottom to permit ionic flux between the internal electrolyte (of the reference electrode) and the external electrolyte. In this work, the copper/copper sulfate reference electrode was modified by replacing the porous ceramic junction plate for a metallic platinum wire. The main purpose of this modification was to avoid the ion copper transport from coming from the inner reference electrode solution into the surrounding electrolyte, and to mitigate the copper plating on the coupon surfaces. Lab tests were performed in order to compare the performance of the two mentioned reference electrodes. We verified that the experimental errors associated with the measurements conducted with developed reference electrode would be negligible, as the platinum surface area exposed to the surrounding electrolyte and/or to the reference electrolyte are maintained as small as possible.

• 한국산학기술학회논문지
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• 제12권1호
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• pp.545-551
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• 2011

최근 고품질의 수돗물에 대한 소비자의 요구가 상승함에 따라 상수도 배급수관의 내부 부식에 의한 수질악화 및 부식제어 연구에 대한 관심이 높아지고 있다. 이에 따라 노후 관 교체 사업을 대신하여 수질 관리를 위한 부식 제어 수단을 강구하지 않고서는 근본적인 문제 해결이 이루어질 수 없는 실정이다. 본 연구에서는 수질안정화 약품 주입에 의한 상수도관 내부 부식제어 효율을 평가하기 위해 Pilot Plant 실험을 실시하였으며, 부식성제어 효율은 물의 부식성을 나타내는 LSI(Langelier Saturation Index)값에 의해 평가되었다. 실험결과, Pilot Plant에 의해 제조된 반응수는 수질안정화 약품인 액상소석회($Ca(OH)_2$, liquid lime)의 주입으로 부식성이 개선되어 철 용출이 억제되는 효과가 확인되었다. 강관과 동관을 절단하여 제작한 시편의 부식도 측정을 통해 각각 35.4, 44.5%의 부식제어 효과가 있음을 확인하였고 수질안정화 약품이 주입된 Sample관이 더 두터운 부식 생성물 층을 갖고 있는 것으로 밝혀졌으며, 결과적으로 수질안정화 약품을 투입한 배관이 부식 방지 측면에서 안정한 수질을 갖고 있음을 알 수 있었다.

• Structural Engineering and Mechanics
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• 제20권3호
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• pp.265-277
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• 2005

This paper is focused on fractal analysis of the surface cracking, a new tool for safety evaluation of corroded reinforced concrete (RC) beams. Comprehensive experimental investigations, including flexural tests, coupon tests on strength evaluation of corroded concrete and rusty rebar, and pullout tests to determine bond strength between concrete and rebar were carried out on nine Corroded Reinforced Concrete Beams (CRCB) exposed to an aggressive environment for more than 10 years. In combination with test results from a previous study on CRCBs fabricated in the laboratory from accelerated methods, it is found that, for both types of beams, the surface cracking distributions are fractal in character at loading and failure stages. Fractal dimension is calculated for all specimens at different corrosion states based on fractal analysis method. Relationships between the fractal dimension and mechanical properties of corroded concrete, rebar corrosion ratio, and ductility of CRCBs are discussed in detail. It is concluded that the fractal dimension can act as a damage index and can be efficiently used to describe the corrosion state of CRCBs.

• Steel and Composite Structures
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• 제12권5호
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• pp.379-393
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• 2012

Many steel bridge infrastructures in the world are getting older, and a large number of these structures are in need of maintenance, rehabilitation or replacement. Most of them are subjected to corrosion due to exposure to aggressive environmental conditions and inadequate maintenance, causing reduction of their carrying capacities. In order to have an adequate bridge management, it is of paramount importance to develop an efficient, accurate and rapid condition assessment method which can be used to make reliable decisions affecting the cost and safety. Therefore, a simple and accurate method of calculating remaining yield and tensile strength by using a concept of representative effective thickness with correlation of initial thickness and maximum corroded depth is proposed in this study, based on the results of many tensile coupon tests of corroded plates obtained from a steel plate girder with severe corrosion, used for about 100 years. Furthermore, a strength reduction diagram which will be very useful for bridge inspection engineers to make rational decisions about the maintenance management of aged steel bridge infrastructures is presented.