한국부식방식학회

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Page : 478 - 483 DOWNLOAD
전자 개폐기용 바이메탈 소재(Fe-Ni / Fe-Ni-Mo)의 부식거동
This study examined the corrosion behavior of bimetal materials composed of Fe-Ni alloy and Fe-Ni-Mo alloy, both suitable for use in electromagnetic switches. Electrochemical polarization and weight loss measurements revealed that, in contrast to Fe-Ni alloy, which exhibited pseudo-passivity behavior, Fe-Ni-Mo alloy had higher anodic current density, displaying only active dissolution and greater weight loss. This indicated a lower corrosion resistance in the Fe-Ni-Mo alloy. Equilibrium calculations for the phase fraction of precipitates suggested that the addition of 1 wt% Mo may lead to the formation of second-phase precipitates, such as Laves and M 6 C, in the γ matrix. These precipitates might degrade the homogeneity of the passive film formed on the surface, leading to localized attacks during the corrosion process. Therefore, considering the differences in corrosion kinetics between these bimetal materials, the early degradation caused by galvanic corrosion should be prevented by designing a new alloy, optimizing heat treatment, or implementing periodic in-service maintenance.
KEYWORDs : Bimetal, Invar, Electromagnetic switches, Molybdenum, Corrosion
AUTHORs : 안유정 · 황은혜 · 전재열† · 김성진†

Page : 466 - 477 DOWNLOAD
전고체 리튬 이차전지용 합금계 음극 소재의 연구 동향
The increasing demand for high-performance energy storage systems has highlighted the limitations of conventional Li-ion batteries (LIBs), particularly regarding safety and energy density. All-solid-state batteries (ASSBs) have emerged as a promising next-generation energy storage system, offering the potential to address these issues. By employing nonflammable solid electrolytes and utilizing high-capacity electrode materials, ASSBs have demonstrated improved safety and energy density. Automotive and energy storage industries, in particular, have recognized the significance of advancing ASSB technology. Although the use of Li metal as ASSB anode is promising due to its high theoretical capacity and the expectation that Li dendrites will not form in solid electrolytes, persistent problems with Li dendrite formation during cycling remain. Therefore, the exploration of novel high-performance anode materials for ASSBs is highly important. Recent research has focused extensively on alloy-based anodes for ASSBs, owing to their advantages of no dendrite formation and high-energy density. This study provides a comprehensive review of the latest advancements and challenges associated with alloy-based anodes for ASSBs.
KEYWORDs : All-solid-state-battery, Anode materials, Alloy-based anode, Li-ion battery, Solid electrolyte
AUTHORs : 윤정명 · 박철민†

Page : 457 - 465 DOWNLOAD
오스테나이트 스테인리스강 저속인장시험편의 최적 전해연마 특성
Irradiation-assisted stress corrosion cracking (IASCC) is one of the main degradation mechanisms of austenitic stainless steels, which are used as reactor internal materials. Slow strain rate testing (SSRT) has been widely applied to evaluate the IASCC initiation characteristics of proton-irradiated tensile specimens. Tensile specimens require low surface roughness for micro-crack observation, and electropolishing is the most important specimen pre-treatment process used for this. In this study, optimal electropolishing conditions were examined through analyzing results of polarization experiments and surface roughness measurements after electropolishing. Corrosion cell and electropolishing equipment were fabricated for polarization tests and electropolishing experiments using SSRT specimens. The experimental parameters were electropolishing time, current density, electrolyte temperature, and stirring speed. The optimal electropolishing conditions for SSRT tensile specimens made of type 316 stainless steel were evaluated as a polishing time of 180 seconds, a current density of 0.15 A/cm 2 , an electrolyte temperature of 60 °C, and a stirring speed of 200 RPM.
KEYWORDs : Electropolishing, Surface roughness, Austenitic stainless steel, SSRT, Polarization
AUTHORs : 최민재 † · 조은별 · 김동진

Page : 447 - 456 DOWNLOAD
고분자전해질 연료전지용 Ti 분리판을 위한 고분자와 Ti Sol-Gel 탄소코팅의 비교 연구
In this work, we performed a comparative study examining two coatings on Ti Gr.1 for use in fuel cell bipolar plates. The coatings consisted of carbon black as the conductor along with acrylic polymer and Ti Sol-Gel binder as the binder. Ti Sol-Gel that had precipitated as TiO2 in areas impregnated between carbon black gaps, thereby acting as a binder for carbon black and serving as a polymer coating. Neither of the coatings peeled off during the 90° bend test to check formability. The contact resistance of the TiO2 coating was found to be lower than that of the polymer binder coating. Moreover, due to coating shrinkage (denser) that occurred during the heat treatment process, the TiO2 binder coating showed almost the same level of corrosion resistance, as measured by potentiostatic and EIS tests, despite being thinner than the polymer coating. However, both the polymer binder coating and the TiO2 binder coating had many pores and irregularities internally (around 10 ~ 100 ㎚) and on the surface (0.1 ~ 2 ㎛). We considered that these pores and irregularities contributed to the lower corrosion resistance.
KEYWORDs : Corrosion, Ti Bipolar plate, Carbon black, Contact resistance, PEMFC
AUTHORs : 양원석†, 이재호, 노희석, 유주현, 박철민, 이수연, 문성모

Page : 435 - 446 DOWNLOAD
화력발전소용 슈퍼 듀플렉스 스테인리스 강(STS 329J4L) 조관 튜브및 핀-튜브재의 부식거동
Corrosion behaviors of laser-welded super duplex stainless steel (SDSS) tubes after exposure to an actual power plant environment for one year and those of fin-tube welded SDSS were evaluated. Results showed that corrosion damage on the back side of the SDSS tube in the direction of hot air was higher than that on the front side regardless of weldment location. However, corrosion damage showed no difference between weldment and base metal due to recovery of phase fraction in the weldment through post weld heat treatment (PWHT). Nevertheless, the SDSS tube showed severe corrosion damage along grain boundary due to surface phase transformation (δ → γ) and Cr 2 N precipitation caused by PWHT with a high N 2 atmosphere. Corrosion resistance of the SDSS tube was recovered when degraded surface was removed. Corrosion sensitivity of a fin-tube increased significantly due to pre-existing crevice, unbalanced phase fraction, and σ phase precipitation adjacent to the fusion line. Although corrosion resistance was improved by recovered phase fraction and sufficient dissolution of σ phase during PWHT, corrosion reaction was concentrated at the pre-existing crevice. These results suggest that welding conditions for fin-tube steel should be optimized to improve corrosion resistance by removing pre-existing crevice in the weldment.
KEYWORDs : Super duplex stainless steel, Corrosion, Fin-tube, Heat treatment, Phase transformation
AUTHORs : 박진성 · 김용현 · 홍승갑 · 김성진†

Page : 429 - 434 DOWNLOAD
UNS G41400 강의 인산염 표면 처리에 따른 국부 부식 저항성
This study investigated the localized corrosion behavior of a UNS G41400 steel surface treated with manganese phosphate. The phosphate coating, primarily composed of oxygen (O), phosphorus (P), and manganese (Mn) elements, had an approximate thickness of 6 µm. The particles comprising the coating varied in size by several micrometers; smaller particles were mainly composed of O, P, Mn, and iron (Fe) elements, indicating incomplete formation of the manganese phosphate film. Potentiodynamic polarization curves revealed a decrease in anodic current after surface treatment and a shift in corrosion potential toward the noble direction after treatment. After immersion in a 3.5 wt% NaCl solution for 96 hours, localized corrosion was observed, with some regions retaining residual phosphate film. Even though localized corrosion occurred on the treated surface, it was less severe than that on the untreated UNS G41400 steel surface. These findings suggest that manganese phosphate coating improved resistance to localized corrosion.
KEYWORDs : Phosphate coating, Corrosion, Steel, Chloride
AUTHORs : 이준섭† · 박시욱

Page : 419 - 428 DOWNLOAD
해수배관 내부 에폭시 코팅재의 캐비테이션 및 침지 열화에 따른 압입인장특성
Seawater has been used to cool devices in nuclear power plants. However, the pipes used to transport seawater are vulnerable to corrosion; hence, the inner side of pipelines is coated with an epoxy layer as prevention. Upon coating damage, the pipe becomes exposed, and corrosion progresses. The major cause is widely known as cavitation corrosion, causing the degradation of mechanical properties. In this study, corroded specimens were prepared using cavitation and immersion methods to clarify the degradation trend of mechanical properties with corrosion. Three different types of epoxy coatings were used, and accelerated cavitation procedures were composed of amplitudes of 15 µm, 50 µm, and 85 µm for 2 h, 4 h, and 6 h. The immersion periods were 3 and 6 weeks. We conducted instrumented indentation tests on all degradation samples to measure mechanical properties. The results showed that higher cavitation amplitudes and longer cavitation or immersion times led to more degradation in the samples, which, in turn, decreased the yield strength. Of the three samples, the C coating had the highest resistance to cavitation and immersion degradation.
KEYWORDs : Cavitation, Epoxy coating, Degradation, Indentation, Stress analysis
AUTHORs : 정민재 · 김수현 · 전종모 · 김영식 · 김영천†

Page : 408 - 418 DOWNLOAD
Effect of Al and Nb Doping on the Electrochemical Characteristics of Garnet-type Li7 La3 Zr2 O12 Solid Electrolytes
In this study, we synthesized and characterized garnet-type Li 7-x Al x La 3 Zr 2-(5/4)y NbyO 12 (LALZN) solid elec-trolytes for all-solid-state battery applications. Our novel approach focused on enhancing ionic conduc-tivity, which is crucial for battery efficiency. A systematic examination found that co-doping with Al and
Nb significantly improved this conductivity. Al 3+ and Nb 5+ ions were incorporated at Li + and Zr 4+ sites, respectively. This doping resulted in LALZN electrolytes with optimized properties, most notably enhanced ionic conductivity. An optimized mixture with 0.25 mol each of Al and Nb dopants achieved a peak conductivity of 1.32 × 10 -4 S cm -1 . We fabricated symmetric cells using these electrolytes and observed excellent charge-discharge profiles and remarkable cycling longevity, demonstrating the potential for long-term application in battery systems. The garnet-type LALZN solid electrolytes, with their high ionic conductivity and stability, show great potential for enhancing the performance of all-solid-state batteries. This study not only advances the understanding of effective doping strategies but also underscores
the practical applicability of the LALZN system in modern energy storage solutions.
KEYWORDs : Solid electrolyte, Garnet, Doping, Ionic conductivity, Solid-state batteries
AUTHORs : Ahmed Tarif and Chan-Jin Park †

Page : 399 - 407 DOWNLOAD
Investigation of Functional 6061 Aluminum Alloy Oxide Film with Anodization Voltage and its Corrosion Resistance
This study investigated the formation of oxide films on 6061 aluminum (Al) alloy and their impacts on corrosion resistance efficiency by regulating anodization voltage. Despite advantageous properties inherent to Al alloys, their susceptibility to corrosion remains a significant limitation. Thus, enhancing corrosion resistance through developing protective oxide films on alloy surfaces is paramount. The first anodization was performed for 6 h with an applied voltage of 30, 50, or 70 V on the 6061 Al alloy. The second anodization was performed for 0.5 h by applying 40 V after removing the existing oxide film. Resulting oxide film’s shape and roughness were analyzed using field emission–scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Wettability and corrosion resistance were compared before and after a self-assembled monolayer (SAM) using an FDTS (1H, 1H, 2H, 2H-Perfluorodecyltrichlorosilane) solution. As the first anodization voltage increased, the final oxide film’s thickness and pore diameter also increased, resulting in higher surface roughness. Consequently, all samples exhibited superhydrophilic behavior before coating. However, contact angle after coating increased as the first anodization voltage increased. Notably, the sample anodized at 70 V with superhydrophobic characteristics after coating demonstrated the highest corrosion resistance performance.
KEYWORDs : Aluminum 6061 alloy, Anodization voltage variation, Corrosion resistance, Superhydrophilicity, Superhydrophobicity
AUTHORs : Jisoo Kim, Chanyoung Jeong†

Page : 393 - 398 DOWNLOAD
Microstructures and Mechanical Properties of HfN Coatings Deposited by DC, Mid-Frequency, and ICP Magnetron Sputtering
Properties of hafnium nitride (HfN) coatings are affected by deposition conditions, most often by the sputtering technique. Appropriate use of different magnetron sputtering modes allows control of the structural development of the film, thereby enabling adjustment of its properties. This study compared properties of HfN coatings deposited by direct current magnetron sputtering (dcMS), mid-frequency direct current magnetron sputtering (mfMS), and inductively coupled plasma-assisted magnetron sputtering (ICPMS) systems. The microstructure, crystalline, and mechanical properties of these HfN coatings were investigated by field emission electron microscopy, X-ray diffraction, atomic force microscopy, and nanoindentation measurements. HfN coatings deposited using ICPMS showed smooth and highly dense microstructures, whereas those deposited by dcMS showed rough and columnar structures. Crystalline structures of HfN coatings deposited using ICPMS showed a single δ-HfN phase, whereas those deposited using dcMS and mfMS showed a mixed δ-HfN and HfN 0.4 phases. Their performance were increased in the order of dcMS < mfMS < ICPMS, with ICPMS achieving a value of 47.0 GPa, surpassing previously reported results.
KEYWORDs : Direct current magnetron sputtering, Mid-frequency magnetron sputtering, Inductively coupled plasma-assisted magnetron sputtering, HfN, Coatings
AUTHORs : Sung-Yong Chun†

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