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Page : 170 - 177
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- Effects of surface modification with hydroxyl terminated polydimethylsiloxane on the corrosion protection of polyurethane coating
- Polyurethane coating was designed to give a hydrophobic property on its surface by modifying it with hydroxyl terminated polydimethylsiloxane and then effects of surface hydrophobic tendency, water transport behavior and hence corrosion protectiveness of the modified polyurethane coating were examined using FT-IR/ATR spectroscopy, contact angle measurement and electrochemical impedance test. As results, the
surface of polyurethane coating was changed from hydrophilic to hydrophobic property due primarily to a phase separation tendency between polyurethane and modifier by the modification. The phase separation tendency is more appreciable when modified by polydimethylsiloxane with higher content. Water transport
behavior of the modified polyurethane coating decreased more in that with higher hydrophobic surface property. The decrease in the impedance modulus |Z| at low frequency region in immersion test for polyurethane coatings was associated with the water transport behavior and surface hydrophobic properties of modified
polyurethane coatings. The corrosion protectiveness of the modified polyurethane coated carbon steel generally increased with an increase in the modifier content, confirming that corrosion protectiveness of the modified polyurethane coating is well agreed with its water transport behavior. - KEYWORDs : polysiloxane, corrosion protection, EIS, polyurethane, FT-IR
- AUTHORs : Jae Hong Jeon and MinYoung Shon†
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Page : 178 - 185
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- Ni-Cr계 고용강화형 합금에서 조성에 따른 기계적 및 고온부식 특성 평가
- Alloy 617 is considered as a candidate Ni-based superalloy for the intermediate heat exchanger (IHX) of a very high-temperature gas reactor (VHTR) because of its good creep strength and corrosion resistance at high temperatures. Helium is used as a coolant in a VHTR owing to its high thermal conductivity, inertness, and low neutron absorption. However, helium inevitably includes impurities that create an imbalance in the surface reactivity at the interface of the coolant and the exposed materials. As the Alloy 617 has been exposed to high temperatures at 950°C in the impure helium environment of a VHTR, the degradation of material is accelerated and mechanical properties decreased. The high-temperature strength, creep, and corrosion properties of the structural material for an IHX are highly important to maintain the integrity in a harsh environment for a 60 year period. Therefore, an alloy superior to alloy 617 should be developed. In this study, the mechanical and high-temperature corrosion properties for Ni-Cr alloys fabricated in the laboratory were evaluated as a function of the grain boundary strengthening and alloying elements. The ductility increased and decreased by increasing the amount of Mo and Cr, respectively. Surface oxide was detached during the corrosion test, when Al was not added to alloy. However the alloy with Al showed improved oxide adhesive property without significant degradation and mechanical property. Aluminum seems to act as an anti-corrosive role in the Ni-based alloy.
- KEYWORDs : VHTR, Ni-Cr alloy, tensile test, high-temperature corrosion, alloying element
- AUTHORs : 정 수 진†·김 동 진
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Page : 178 - 185
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- Ni-Cr계 고용강화형 합금에서 조성에 따른 기계적 및 고온부식 특성 평가
- Alloy 617 is considered as a candidate Ni-based superalloy for the intermediate heat exchanger (IHX) of a very high-temperature gas reactor (VHTR) because of its good creep strength and corrosion resistance at high temperatures. Helium is used as a coolant in a VHTR owing to its high thermal conductivity, inertness, and low neutron absorption. However, helium inevitably includes impurities that create an imbalance in the surface reactivity at the interface of the coolant and the exposed materials. As the Alloy 617 has been exposed to high temperatures at 950°C in the impure helium environment of a VHTR, the degradation of material is accelerated and mechanical properties decreased. The high-temperature strength, creep, and corrosion properties of the structural material for an IHX are highly important to maintain the integrity in a harsh environment for a 60 year period. Therefore, an alloy superior to alloy 617 should be developed. In this study, the mechanical and high-temperature corrosion properties for Ni-Cr alloys fabricated in the laboratory were evaluated as a function of the grain boundary strengthening and alloying elements. The ductility increased and decreased by increasing the amount of Mo and Cr, respectively. Surface oxide was detached during the corrosion test, when Al was not added to alloy. However the alloy with Al showed improved oxide adhesive property without significant degradation and mechanical property. Aluminum seems to act as an anti-corrosive role in the Ni-based alloy.
- KEYWORDs : VHTR, Ni-Cr alloy, tensile test, high-temperature corrosion, alloying element
- AUTHORs : 정 수 진†·김 동 진
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Page : 186 - 194
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- 돌리를 이용한 도막 부착력 시험의 영향 인자에 관한 연
- Establishment of adhesion strength measurement procedure for marine epoxy coatings was conducted in order to ensure reliability of the test results. It was found that (1) the increase in thickness of the substrates would induce increase of pull-off strength. Especially, the increase in adhesion strength with the substrate thickness increment was attributed to the transition of stress mode to the pure tensile mode excluding bending effect. (2) The longer curing time, the higher pull-off strength. It may be due to higher cross-linking density of the coating (3) The pull-off strength increases as coating thickness increases due to the diminishment of bending effect (4) The longer drying time after water immersion, the higher pull-off strength. It may
be due to the evaporation of water molecule at the coating-substrate interface. - KEYWORDs : coating, pull-off strength, epoxy, polyamide
- AUTHORs : 백 윤 호†·손 성 모·박 충 서
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Page : 186 - 194
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- 다양한 금속 부품의 내식성 향상을 위한 Zn-Al 열 확산 코팅 기술 개발
- Modern industry has a wide variety of application areas such as ocean industry, construction and automobile industry. With the current circumstances, the need for anti-corrosion technology that can be used on materials to withstand in harsh environments, is increasing. In this study, we have sought to develop a metal coating
technology with zinc and aluminum powders as a potential anti-corrosion material. To make a coating on metal products, a thermal diffusion coating method was used under the conditions of 350℃ for 30 minutes. Optical microscope, Field emission scanning electron microscope (FE-SEM&EDX) and X-ray diffraction analysis were used to analyze a coating layer. As a result, we have confirmed that the generated amount of rust on metal parts coated with thermal diffusion coating method decreased dramatically compared with non-coated metal parts. Furthermore, the anti-corrosion performance was evaluated according to the different ratio of zinc and aluminum. Finally, we confirmed the possibility of application and commercialization
of our coating technique on metal parts used in harsh industrial based on the results of these performance. - KEYWORDs : anti-corrosion, metal products, Zinc-Aluminum, thermal diffusion coating
- AUTHORs : 이 주 영·이 주 형·황 준·이 용 규†
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Page : 209 - 213
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- Resistance to Corrosion of Reinforcement of High Volume Fly Ash Concrete
- Due to the increasing of interest about the eco-friendly concrete, it is increased to use concretes containing by-products of industry such as fly ash(FA), ground granulated blast furnace slag(GGBFS), silica fume(SF), and etc. Especially, these are well known for improving the resistances to reinforcement corrosion in concrete
and decreasing chloride ion penetration. The purpose of this experimental research is to evaluate the resistance against corrosion of reinforcement of high volume fly ash(HVFA) concrete which is replaced with high volume fly ash for cement volume. For this purpose, the concrete test specimens were made for various strength level and replacement ratio of FA, and then the compressive strength and diffusion coefficient
for chloride ion of them were measured for 28, 91, and 182 days, respectively. Also, corrosion monitoring by half cell potential method was carried out for the made lollypop concrete test specimens to detect the time of corrosion initiation for reinforcement in concrete. As a result, it was observed from the test results
that the compressive strength of HVFA concrete was decreased with increasing replacement ratio of FA but long-term resistances against reinforcement corrosion and chloride ion penetration of that were increased. - KEYWORDs : high volume fly ash concrete, corrosion of reinforcement, monitoring, resistance to chloride ion penetration
- AUTHORs : S. O. Kwon, S. H. Bae†, H. J. Lee, K. M. Lee, and S. H. Jung
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Page : 214 - 223
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- 염해 및 복합열화에 의한 부식촉진시험과 장기폭로 시험의 상관성에 관한 연구
- Interest in the durability assessment and structural performance has increased according to an increase of concrete structures in salt damage environment recent years. Reliable way ensuring the most accelerated corrosion test is a method of performing the rebar corrosion monitoring as exposed directly to the marine test site exposure. However, long-term exposure test has a disadvantage because of a long period of time. Therefore, many studies on reinforced concrete in salt damage environments have been developed as alternatives to replace this. However,
accelerated corrosion test is appropriate to evaluate the critical chlorine concentration in the short term, but only accelerated test method, is not easy to get correct answer. Accuracy of correlation acceleration test depends on the period of the degree of exposure environments. Therefore, in this study, depending on the concrete mix material, by the test was performed on the basis of the composite degradation of the salt damage, and investigate the difference of corrosion initiation time of the rebar, and indoor corrosion time of the structure, of the marine
environment of the actual environments were inuestigated. The correlation coefficient was derived in the experiment. Long-term exposure test was actually conducted in consideration of the exposure conditions submerged zone, splash zone and tidal zone. The accelerated corrosion tests were carried out by immersion conditions, and by the combined deterioration due to the carbonation and accelerated corrosion due to wet and dry condition. - KEYWORDs : durability, accelerated corrosion test, salt damage, neutralization test, tidal zone
- AUTHORs : 박상순†·이민우
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Page : 224 - 232
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- 전처리가 그래핀을 코팅한 고체고분자 연료전지 분리판의 전기화학적 특성에 미치는 영향
- Effect of pretreatments on the graphene coated bipolar plate of proton exchange membrane fuel cell(PEMFC) was investigated in simulated environments for PEMFC by using electrochemical measurement techniques. Interfacial contact resistance(ICR) between the graphene coated bipolar plate and the gas diffusion layer(GDL)
was measured. The value of ICR decreased with an increase in compaction stress(20N/cm2~220N/cm2). ICR of graphene coated bipolar plate was higher than that of bare 316L stainless steel. However, Potentiodynamic measurement results showed that the corrosion resistance of graphene coated bipolar plate was higher than that of bare 316L stainless steel. H2SO4 acid pretreatment was the most effective among various pretreatments. The lowest ICR and the corrosion current density were obtained when using H2SO4 solution pretreatment. - KEYWORDs : PEMFC, bipolar plate, graphene, stainless steel, interfacial contact resistance, corrosion resistance
- AUTHORs : 차성윤·이재봉†
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Page : 1 - 11
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- THINNED PIPE MANAGEMENT PROGRAM OF KOREAN NUCLEAR POWER PLANTS
- Local wall thinning and integrity degradation caused by several mechanisms, such as flow accelerated corrosion (FAC), cavitation, flashing and/or liquid drop impingements, are a main concern in carbon steel piping systems of nuclear power plant in terms of safety and operability. Thinned pipe management program (TPMP)
had been developed and optimized to reduce the possibility of unplanned shutdown and/or power reduction due to pipe failure caused by wall thinning in the secondary side piping system. This program also consists of several technical elements such as prediction of wear rate for each component, prioritization of components
for inspection, thickness measurement, calculation of actual wear and wear rate for each component. Decision making is associated with replacement or continuous service for thinned pipe components. Establishment of long-term strategy based on diagnosis of plant condition regarding overall wall thinning is also essential
part of the program. Prediction models of wall thinning caused by FAC had been established for 24 operating nuclear plants. Long term strategies to manage the thinned pipe component were prepared and applied to each unit, which was reflecting plant specific design, operation, and inspection history, so that the structural integrity of piping system can be maintained. An alternative integrity assessment criterion and a computer program for thinned piping items were developed for the first time in the world, which was directly applicable
to the secondary piping system of nuclear power plant. The thinned pipe management program is applied to all domestic nuclear power plants as a standard procedure form so that it contributes to preventing an accident caused by FAC. - KEYWORDs : flow accelerated corrosion, wall thinning, prediction model, integrity assessment
- AUTHORs : S. H. Lee†, Y. S. Lee, S. K. Park, and J. G. Lee
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Page : 12 - 18
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- REAL-TIME CORROSION CONTROL SYSTEM FOR CATHODIC PROTECTION OF BURIED PIPES FOR NUCLEAR POWER PLANT
- Since the operation period of nuclear power plants has increased, the degradation of buried pipes gradually increases and recently it seems to be one of the emerging issues. Maintenance on buried pipes needs high quality of management system because outer surface of buried pipe contacts the various soils but inner surface reacts with various electrolytes of fluid. In the USA, USNRC and EPRI have tried to manage the degradation of buried pipes. However, there is little knowledge about the inspection procedure, test and manage program in the domestic nuclear power plants. This paper focuses on the development and build-up of real-time monitoring and control system of buried pipes. Pipes to be tested are tape-coated carbon steel
pipe for primary component cooling water system, asphalt-coated cast iron pipe for fire protection system, and pre-stressed concrete cylinder pipe for sea water cooling system. A control system for cathodic protection was installed on each test pipe which has been monitored and controlled. For the calculation of protection
range and optimization, computer simulation was performed using COMSOL Multiphysics (Altsoft co.). - KEYWORDs : nuclear power plant, buried pipe, cathodic protection, design, computer simulation
- AUTHORs : Ki Tae Kim, Hae Woong Kim, Young Sik Kim,†, Hyun Young Chang, Bu Taek Lim, and Heung Bae Park
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