한국부식방식학회

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Page : 387 - 392 DOWNLOAD
일상 생활용수 내 Zn-Al-Mg계 합금도금강재의 부식거동
The objective of this study was to evaluate corrosion resistance of Zn-Al-Mg alloy coated steel in residential water with trace quantities of Cl - . Comparative evaluations were performed using two commercial coated steel products, GI and Galvalume, as reference samples. Examination of corrosion morphology and measurement of weight loss revealed that the Zn-Al-Mg alloy coated steel exhibited higher corrosion resistance than reference samples. This finding suggests that the alloy coated steel possesses long-term corrosion resistance not only in highly Cl - concentrated environments such as seawater, but also in environments with extremely low levels of Cl - found in residential water. The primary factor contributing to the superior corrosion resistance of the Zn-Al-Mg alloy coated steel in residential water is the formation of an inhibiting corrosion product composed primarily of two phases: Zn 5 (OH) 6 (CO 3 ) 2 and Zn 5 (OH) 8 Cl 2 ·H 2 O. The preferential dissolution of Mg from the corroded coating layer can increase alkalinity, which might
enhance the thermodynamical stability of Zn 5 (OH) 6 (CO 3 ) 2.
KEYWORDs : Zn-Al-Mg alloy coated steel, Corrosion, Tap water, Residential water, Corrosion product
AUTHORs : 이재원 · 김성진†

Page : 377 - 386 DOWNLOAD
인공신경망과 대기부식환경 모니터링 데이터를 이용한 항공기 세척주기 결정 알고리즘
Aircraft washing is performed periodically for corrosion control. Currently, the aircraft washing interval is qualitatively set according to the geographical conditions of each base. We developed a washing interval determination algorithm based on atmospheric corrosion environment monitoring data at the Republic of Korea Air Force (ROKAF) bases and United States Air Force (USAF) bases to determine the optimal interval. The main factors of the washing interval decision algorithm were identified through hierarchical clustering, sensitivity analysis, and analysis of variance, and criteria were derived. To improve the classification accuracy, we developed a washing interval decision model based on an artificial neural network (ANN). The ANN model was calibrated and validated using the atmospheric corrosion environment monitoring data and washing intervals of the USAF bases. The new algorithm returned a three-level washing interval, depending on the corrosion rate of steel and the results of the ANN model. A new base-specific aircraft washing interval was proposed by inputting the atmospheric corrosion environment monitoring results of the ROKAF bases into the algorithm.
KEYWORDs : Atmospheric corrosion, Artificial neural network (ANN), Aircraft wash interval
AUTHORs : 권혁준 · 이두열†

Page : 368 - 376 DOWNLOAD
치과용 Ni-Ti파일의 표면특성에 미치는 ta-C코팅효과
Dental Ni-Ti files must ensure stability and resistance to fatigue fracture. DLC and ta-C were coated to remove defects on the surface and ensure stability, and the surface characteristics were investigated. When coated with DLC, it was black, and in case of ta-C coating, it was blue-black. Scratches, which are defects caused by mechanical processing, were formed on the surface of the un-coated Ni-Ti file from the end of the file along the direction of processing, with the Pro-file appearing in the vertical direction and the K-file appearing in the file direction. Scratches were reduced on the coated surface, and the surface roughness was greatly reduced after coating compared to before coating. The un-coated Ni-Ti file had the lowest hardness, the DLC-coated file had the highest hardness, and ta-C showed relatively high hardness. The elastic modulus of the DLC coating film was high, and the ta-C elastic modulus was low. The adhesion of the DLC coating film tended to be higher than that of ta-C, and the wear loss amount of DLC coating of taC was lower. The corrosion potential of the ta-C coating increased significantly, and the corrosion current density decreased.
KEYWORDs : Ni-Ti file, DLC, ta-C, Corrosion resistance, Mechanisal properties
AUTHORs : 박순균 · 최한철†

Page : 359 - 367 DOWNLOAD
Inconel 718의 국부 부식 저항성에 미치는 용체화 열처리의 영향
The localized corrosion resistance of the Ni-based Inconel 718 alloy after solution heat treatment was evaluated using electrochemical techniques in a solution of 25 wt% NaCl and 0.5 wt% acetic acid. Solution heat treatment at 1050o C for 2.5 hours resulted in an increased average grain diameter. Both Ti carbides (10 µm diameter) and Nb-Mo carbides (1 – 9 µm diameter) were distributed throughout the material.
Despite heat treatment, the shape and composition of these carbides remained consistent. An increase in solution temperature led to a decrease in pitting potential value. However, the pitting potential value of solution heat-treated Inconel 718 was consistently higher than that of as-received Inconel 718 at all tested temperatures. Localized corrosion initiation occurred at 0.4 V SSE in a temperature environment of 80 o C for both as-received and solution heat-treated Inconel 718 alloys. X-ray photoelectron spectroscopic analysis indicated that the composition of the passive film formed on specimen surfaces remained largely unchanged after solution heat treatment, with O1s, Cr2p 3/2 , Fe2p 3/2 , and Ni2p 3/2 present. The difference in localized corrosion resistance between as-received and solution heat-treated Inconel 718 alloys was attributable to microstructural changes induced by the heat treatment process.
KEYWORDs : Inconel, Heat treatment, Passivity, Corrosion, Acidic chloride
AUTHORs : 이윤화 · 이준섭† · 권순일 · 신정호 · 이재현

Page : 351 - 358 DOWNLOAD
발전소 공기예열기 소재의 배기가스 농도 및 온도에 따른 내식성 및 노점 분석
Although many thermal power plants use heat recovery systems, high exhaust gas temperatures are maintained due to corrosion at dew points and ash deposits caused by condensate formation. The dew point of exhaust gas is primarily determined by the concentration of SO 3 and steam, and various experiments and cal-culation equations have been employed to estimate it. However, these methods are known to be less suitable for exhaust gases with low SO 3 concentrations. Therefore, in this study, since the temperature of the exhaust gas is expected to decrease due to the low-load operation of the coal-fired power plant, sulfuric acid condensation and low-temperature corrosion are anticipated. We aimed to conduct a quantitative evaluation to propose ways to prevent damage by limiting operating conditions and improving facilities. The experimental results showed that the corrosion rate increased linearly with rising temperatures at a certain sulfuric acid concentration. Furthermore, variations in sulfuric acid concentrations generated during the current power plant operation process did not significantly affect the dew point, and the dew point of sulfuric acid under these conditions was observed to be between 120 - 130o C.
KEYWORDs : Corrosion, Dew point, SO 2 , Air preheater, S-Ten2
AUTHORs : 이승준†

Page : 341 - 350 DOWNLOAD
Zn-Flash 코팅 처리가 전기아연도금 시 초고강도 강재의 수소 발생, 유입 및 취화 거동에 미치는 영향
In the present study, effects of a thin Zn-flash coating on hydrogen evolution, infusion, and embrittlement of advanced high strength steel during electro-galvanizing were examined. The electrochemical permeation technique in conjunction with impedance spectroscopy was employed under applied cathodic polarization. Moreover, a slow-strain rate test was conducted to evaluate loss of elongation (i.e., indicative of hydrogen embrittlement (HE)) and examine fracture surfaces. Results showed that the presence of a thin Zn-flash coating, even when it was not distributed uniformly, reduced hydrogen evolution rate and substantially impeded infusion of hydrogen into the steel substrate. This was primarily due to a hydrogen overvoltage on Zn coating and trapping of hydrogen at the interface of Zn coating/flash coating/steel substrate. Consequently, the sample with flash coating had a smaller HE index than the sample without flash coating. These results suggest that a thin Zn-flash coating could be an effective technical strategy for mitigating HE in advanced high-strength steels.
KEYWORDs : Advanced high strength steel, Zn-flash coating, Electro-galvanizing, Hydrogen evolution, Hydrogen embrittlement
AUTHORs : 방혜린 · 김상헌 · 김성진†

Page : 330 - 340 DOWNLOAD
Relationship Between Properties Degradation and Critical Aging Time of Super Austenitic and Duplex Stainless Steels
The objective of this study was to analyze effects of aging time on property degradation of super austenitic stainless steel of PRE 52.8 and super duplex stainless steel of PRE 48.7. To analyze corrosion properties based on aging time, a critical pitting temperature test was performed in a solution of 6% FeCl 3 + 1% HCl
and an anodic polarization test was performed in deaerated 0.5N HCl + 1N NaCl solution at a temperature of 50 o C. Surface hardness was measured to analyze mechanical properties. It was found that corrosion properties and mechanical properties deteriorated rapidly as aging time increased. Critical pitting temperature had the most effect on critical aging time at which property changes occurred rapidly, followed by pitting potential and hardness. This trend was found to be closely related to the fraction of sigma phase. Rate of sigma phase formation was found to be significantly faster in duplex stainless steel than in austenitic stainless steel.
KEYWORDs : Critical aging time, CPT, Pitting potential, Hardness, Sigma fraction
AUTHORs : S. H. Choi, Y. R. Yoo†, S. Y. Won, G. B. Kim, and Y. S. Kim†

Page : 322 - 329 DOWNLOAD
Galvanic Corrosion Between Component Parts of Aluminum Alloys for Heat Exchanger of Automobile
There are a variety of heat exchangers used in automobiles, such as shell and tube heat exchangers, double tube heat exchangers, and plate heat exchangers. Most of them are water-cooled to prevent engine overheating. There have been reports of corrosion damage to these heat exchangers due to continuous wetting caused by external temperature differences, road pollutants, and snow removal. In addition, galvanic corrosion, which occurs when two dissimilar materials come into contact, has been identified as a major cause. In this study, corrosion characteristics and galvanic corrosion behavior of Al alloy (AA3003, AA4045 and AA7072) used in automobile heat exchangers were analyzed. Effective clad materials for heat exchanger tubes and fins were also evaluated. It was found that AA7072 should be applied as the cladding material for fin AA3003 and that AA4045 was suitable as a cladding material for tube AA3003 because this clad materials application was the most effective clad design to delay the occurrence of pinhole in the tube. Main factors influencing galvanic corrosion dissolution were found to be galvanic corrosion potential difference and galvanic corrosion current density.
KEYWORDs : Heat exchanger, Aluminum alloys, Galvanic corrosion, Clad materials, Sacrificial anode
AUTHORs : Y. R. Yoo, D. H. Kim, G. B. Kim, S. Y. Won, S. H. Choi, and Y. S. Kim†

Page : 314 - 321 DOWNLOAD
Evaluation of Inhibition Efficiency of Thymus Extract as a Corrosion Inhibitor of Aluminum Alloy 5083 in an Ethylene Glycol/NaCl Corrosive Medium
The aim of the present study was to investigate the effect of thymus extract on corrosion inhibition of aluminum 5083 alloy in a 0.1 M NaCl medium prepared using a mixture of ethylene glycol and water using potentiodynamic and electrochemical impedance spectroscopy (EIS) techniques. The potentiodynamic electrochemical technique showed an increase in corrosion inhibition efficiency starting from 49.63% at a concentration of 0.25 g/L to 92.71% at a maximum concentration of 1.25 g/L of the extract. These results were consistent with those obtained via EIS analysis. Spectral characterization of the tested plant extract using the Fourier-transform infrared spectroscopy (FTIR) technique confirmed the presence of organic compounds having different oxygen and aromatic functionalities in the extract that could help enhance the adsorption of these compounds on the aluminum surface. This study reveals possible adsorption isotherm of the thymus extract on the aluminum surface, supporting a Langmuir isotherm for the adsorption of inhibitor molecules on this surface.
KEYWORDs : Thymus extract, Inhibition efficiency, Aluminum alloy, Ethylene glycol, Electrochemical impedance
AUTHORs : H. Hachelef, R. Mehdaoui, K. Hachama, M. Amara, A. Khelifa, A. Benmoussat, M. Hadj Meliani†, and Rami K. Suleiman†

Page : 305 - 313 DOWNLOAD
Effects of Corrosion Inhibitor on Corrosion of Al-based Alloys in Ethylene Glycol-Water Coolant Environment
The objective of this study was to investigate the effectiveness of sodium dodecyl benzene sulfonate (SDBS) as a corrosion inhibitor on the pitting corrosion behavior of aluminum alloys used in electric vehicle battery cooling systems within a mixture of ethylene glycol and water (EG-W) coolant. Potentiodynamic polarization testing revealed unstable passive film formation on the aluminum alloys in the absence of SDBS. However, the addition of SDBS resulted in a robust passive film, enhancing the pitting corrosion resistance across all examined alloys. Pitting corrosion was predominantly observed near intermetallic compounds in the presence of Cl? ions, which was attributed to galvanic interactions. Among tested alloys, A1040 demonstrated superior resistance due to its lower areal fraction of precipitates and donor density. The incorporation of SDBS inhibitors mitigated the overall pitting corrosion process by hindering Cl? ion penetration. These findings suggest that SDBS can significantly improve pitting corrosion resistance in aluminum alloys employed in battery coolant environments.
KEYWORDs : Battery cooling system, Aluminum alloys, Corrosion inhibitor, Intermetallic compounds, Pitting corrosion
AUTHORs : Gwang-Soo Choi, Young-Man Kim† , and Chan-Jin Park†

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