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Page : 163 - 170
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- Determining Factors for the Protectiveness of the Passive Film of FeCrN Stainless Steel Formed in Sulfuric Acid Solutions
- In NaCl solutions acidified with H₂SO₄, Fe20Cr1.1N alloy showed enhanced pitting corrosion resistance than Fe20Cr alloy. An XPS analysis revealed that the passive film of Fe20Cr1.1N alloy contained higher cationfraction of Cr than that of Fe20Cr alloy, and nitrogen was incorporated into the film. In addition, it was found that the passive film of Fe20Cr1.1N alloy was thinner and had higher oxygen vacancy density than that of Fe20Cr alloy. Based on these observations, it was concluded that the chemical composition was the determining factor for the protectiveness of the passive film of Fe20Cr based alloy in dilute H₂SO₄ solution.
- KEYWORDs : stainless steel, nitrogen, sulfuric acid solution, passive film, Mott-Schottky, XPS
- AUTHORs : 하헌영†, 이태호
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Page : 171 - 178
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- Corrosion characteristics and interfacial contact resistances of TiN and CrN coatings deposited by PVD on 316L stainless steel for polymer electrolyte membrane fuel cell bipolar plates
- In a polymer membrane fuel cell stack, the bipolar plate is a key element because it accounts for over 50% of total costs of the stack. In order to lower the cost of bipolar plates, 316L stainless steels coated with nitrides such as TiN and CrN by physical vapor deposition were investigated as alternative materials for the replacement of traditional brittle graphite bipolar-plates. For this purpose, interfacial contact resistances were measured and electrochemical corrosion tests were conducted. The results showed that although both TiN and CrN coatings decreased the interfacial contact resistances to less than 10 mΩ·cm2, they did not significantly improve the corrosion resistance in simulated polymer electrolyte membrane fuel cell environments. A CrN coating on 316L stainless steel showed better corrosion resistance than a TiN coating did, indicating the possibility of using modified CrN coated metallic bipolar plates to replace graphite bipolar plates.
- KEYWORDs : Fuel cell, Bipolar plate, Stainless steel, CrN, TiN, PEMFC
- AUTHORs : 이재봉†, 오인환
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Page : 179 - 184
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- 배관 침부식 손상 연속모사 장비 개발 및 실증
- Pipe wall thinning caused by erosion and corrosion can adversely affect the operation of aged nuclear power plants. Some injured workers owing to pipe rupture has been reported and power reduction caused by unexpected pipe damage has been occurred consistently. Therefore, it is important to develop erosion-corrosion damage prediction model and investigate its mechanisms. Especially, liquid droplet impingement erosion(LDIE) is regarded as the main issue of pipe wall thinning management. To investigate LDIE mechanism with corrosion environment, we developed erosion-corrosion damage simulation apparatus and its capability has been verified through the preliminary damage experiment of 6061-Al alloy. The apparatus design has been based on ASTM standard test method, G73-10, that use high-speed rotator and enable to simulate water hammering and droplet impingement. The preliminary test results showed mass loss of 3.2% in conditions of peripheral speed of 110m/s, droplet size of 1mm-diameter, and accumulated time of 3 hours. In this study, the apparatus design revealed feasibility of LDIE damage simulation and provided possibility of accelerated erosion-corrosion damage test by controlling water chemistry.
- KEYWORDs : erosion, corrosion, liquid droplet impingement, damage, pipe
- AUTHORs : 남원창·류경하†·김재형
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Page : 185 - 190
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- 전기도금법으로 만든 니켈-티타니아 복합체에서 초음파 처리가 도금층에 미치는 영향 연구
- In the present study, Ni-TiO₂composite coatings were electrodeposited in a sulfamate bath containing TiO₂particles. The influence of the ultrasonic treatment on the co-deposition of TiO₂particles in the coating and the hardness of the electrodeposited Ni-TiO₂composite has been investigated. Three different ultrasonic treatments (pretreatment before the electrodeposition (pre-UT), pretreatment + applied during the electrodeposition (UT), and the electrodeposition without the ultrasonic treatment (w/o UT)) were performed. The Ni-TiO₂composite coatings are characterized using scanning electron microscopy (SEM), image analyzer, and hardness tester. Comparison of results indicates that the volume fraction is more important factor than the agglomerated particle size in terms of the strength improvement, and the strength of the electrodeposited Ni-TiO₂composite coatings is enhanced with pre-UT condition.
- KEYWORDs : electro-co-deposition, ultrasonic treatment, volume fraction, current efficiency, particle agglomeration
- AUTHORs : 김명진†·김정수·김동진·김홍표·황성식
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Page : 191 - 197
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- 밀폐 박스거더형 무도장 내후성강 교량의 부식취약부에 대한 방식대책 연구(Ⅱ)
- his study is the second stage of developing the corrosion control technical manual about unpainted weathering steel bridge with closed box girder structures.
This paper contains selection of corrosive sealant to apply into crevice of upper flange, injecting test of sealant at mock-up equipment with various condition, evaluation of experiment result.
Through the experiment of injection of sealants into crevice of mock-up equipment, it is proved that the tar sealant injecting corrosion control method is useful to protect corrosion at box girder upper flange corroded by remaning rain water with calcium chloride.
- KEYWORDs : unpainted weathering steel, splice connection part, electrochemical corrosion, corrosion sensitive area, multi-function sealant
- AUTHORs : 송창영†·이의호·이제현·박현출·최재석·노영태
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Page : 203 - 208
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- A Study on Kaolin and Titanium dioxide affecting Physical Properties of Electrocoating
- The electrocoating for automotive bodies is pigmented with a mixture of titanium dioxide and kaolin. In this study, the effects of titanium dioxide and kaolin contents in coating on electrodeposition process, drying, and surface properties such as surface roughness, gloss, impact resistance and corrosion resistance were investigated. Titanium dioxide and kaolin in coating do not have a decisive effect on curing reaction during drying and corrosion resistance but on gloss, surface roughness, impact resistance and electrodeposition process of coating. According to its size and shape on coating surface, pigment contents increased during drying process. However, the contents of kaolin and TiO2 in coating didn\'t affect the corrosion resistance on zinc phosphated substrate, and the curing properties.
- KEYWORDs : titanium dioxide, kaolin, cataphoretic coating, pigment , extention pigment
- AUTHORs : 양원석†, 황운석
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Page : 209 - 214
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- 0.5wt% 탄소강을 이용한 해안 야외부식시험과 염수분무시험,가속부식시험의 가속계수에 대한 연구
- In the industry, accelerated corrosion test is used for the life time prediction. When anti-corrosion test proceeds in real environments, it is difficult that we predict and evaluate the corrosion life time because of the long test time such as 10 years or more time. Accelerated corrosion test and Salt spray test are able to test corrosion life time of products in the laboratory instead of outdoor corrosion test. Experimental procedure is selected for the corrosion standard specimen, exposure of the specimens, measurements of the mass loss and evaluating the mass loss data. As a result, the acceleration factor of the accelerated corrosion test to the outdoor corrosion test is 414.8. Therefore we can predict the corrosion life time of carbon steel during a short time period.
- KEYWORDs : outdoor corrosion test, salt spray test, accelerated corrosion test, cyclic corrosion test, acceleration factor
- AUTHORs : 조의열†·권기봉·조대형·김종렬
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Page : 215 - 219
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- 수화과정에서 전처리가 알루미늄 합금의 용출에 미치는 효과
- Aluminum alloy(3003) can be dissolved during hydration process with hot tap water. In order to increase the stability of aluminum alloy, it was pretreated with anodization and phosphoric acid before hydration process. The effect of pretreatment on the surface property changes was analyzed with X-ray Photoelectron Spectroscopy (XPS) and Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES) and their results supported that the increase of hydroxyl group (-OH) on the surface formed during anodization and phosphorous acid treatment prevented the dissolution of aluminum alloy during hydration process at high temperature.
- KEYWORDs : aluminum alloy 3003, hydration, anodization, phosphoric acid, XPS, ICP-OES
- AUTHORs : 이병구·이호연·탁용석†
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Page : 220 - 226
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- 전기화학적 노이즈 저항 측정에서의 불확도 평가
- The uncertainty in statistical noise resistance measurement was evaluated for a type 316 stainless steel in NaCl solutions at room temperature. Sensitivity coefficients were determined for measurands or variables such as NaCl concentration, pH, solution temperature, surface roughness, inert gas flow rate and bias potential amplitude. The coefficients were larger for the variables such as NaCl concentration, pH, inert gas flow rate and solution temperature, and they were the major factors increasing the combined standard uncertainty of noise resistance.However, the contribution to the uncertainty in noise resistance measurement from the above variables was remarkably low compared to that from repeated measurements of noise resistance, and thus, it is difficult to lower the uncertainty in noise resistance measurement significantly by lowering the uncertainties related with NaCl concentration, pH, inert gas flow rate and solution temperature. In addition, the uncertainty in noise resistance measurement was high amounting to 17.3 % of the mean, indicating that the reliability in measurement of noise resistance is low.
- KEYWORDs : electrochemical noise, noise resistance, uncertainty, sensitivity coefficient
- AUTHORs : 김종집†·강수연
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Page : 227 - 232
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- 주증기계통 오리피스 후단 소구경 배관의 감육 및 누설 발생
- A number of components installed in the secondary system of nuclear power plants are exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), Cavitation, Flashing, and LDIE (Liquid Droplet Impingement Erosion). Those aging mechanisms can lead to thinning of the components. In April 2013, one (1) inch small bore piping branched from the main steam line experienced leakage resulting from wall thinning in a 1,000 MWe Korean PWR nuclear power plant. During the normal operation, extracted steam from the main steam line goes to condenser through the small bore piping. The leak occurred in the downstream of an orifice. A control valve with vertical flow path was placed on in front of the orifice. This paper deals with UT (Ultrasonic Test) thickness data, SEM images, and numerical simulation results in order to analyze the extent of damage and the cause of leakage in the small bore piping. As a result, it is concluded that the main cause of the small bore pipe wall thinning is liquid droplet impingement erosion. Moreover, it is observed that the leak occurred at the reattachment point of the vortex flow in the downstream side of the orifice.
- KEYWORDs : liquid droplet impingement erosion, wall thinning, scanning electron microscope, computational fluid dynamic
- AUTHORs : 황경모†
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