한국부식방식학회

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Page : 297 - 303 DOWNLOAD
소성인장변형 몇 아연도금된 Fe-Mn-C계 TWIP 강의 전기화학적 수소투과거동
This study aimed to evaluate hydrogen permeation behaviors of pre-strained twinning-induced plasticity steel with or without Zn coating using electrochemical permeation technique. In contrast to un-strained and 30% strained samples, permeation current density was measured in the 60% strained sample. Tensile prestraining at 60% involved microstructural modifications, including a high level of dislocation density and stacking fault with a semi-coherent twin boundary, which might provide a high diffusion path for hydrogen atoms. However, reproducibility of measurements of hydrogen permeation current was low due to nonuniform deformation and localized stress concentration. On the other hand, the permeation current was not measured in pre-strained TWIP steel with Zn coating. Instead, numerous blisters with some cracks were observed on the surface of the coating layer. In locally damaged Zn coating under tensile straining, hydrogen atoms could relatively easily permeate through the coating layer. However, they were trapped at the interface between the coating layer and the substrate, which might delay hydrogen penetration into the steel substrate.
KEYWORDs : Tensile strain, TWIP steel, Hot-dip galvanizing, Hydrogen permeation
AUTHORs : 김성진 †

Page : 287 - 296 DOWNLOAD
리튬금속과 고체전해질의 계면 반응
Li-ion batteries have been gaining increasing importance, driven by the growing utilization of renewable energy and the expansion of electric vehicles. To meet market demands, it is essential to ensure high energy density and battery safety. All-solid-state batteries (ASSBs) have attracted significant attention as a potential solution. Among the advantages, they operate with an ion-conductive solid electrolyte instead of a liquid electrolyte therefore significantly reducing the risk of fire. In addition, by using high-capacity alternative electrode materials, ASSBs offer a promising opportunity to enhance energy density, making them highly desirable in the automotive and secondary battery industries. In ASSBs, Li metal can be used as the anode, providing a high theoretical capacity (3860 mAh/g). However, challenges related to the high interfacial resistance between Li metal and solid electrolytes and those concerning material degradation during charge-discharge cycles need to be addressed for the successful commercialization of ASSBs. This review introduces and discusses the interfacial reactions between Li metal and solid electrolytes, along with research cases aiming to improve these interactions. Additionally, future development directions in this field are explored.
KEYWORDs : Interfacial reaction, Li metal, Solid electrolyte, All-solid-state battery
AUTHORs : 김재헌†

Page : 273 - 286 DOWNLOAD
Corrosion of Steel Rebar in Concrete: A Review
Rebar is embedded in concrete to create reinforced concrete (RC). Rebar carries most of the tensile stress and gives compressively loaded concrete fracture resistance. However, embedded steel corrosion is a significant cause of concern for RC composite structures worldwide. It is one of the biggest threats to concrete structures\' longevity. Due to environmental factors, concrete decays and reinforced concrete buildings fail. The type and surface arrangement of the rebar, the cement used in the mortar, the dosing frequency of the concrete, its penetrability, gaps and cracks, humidity, and, most importantly, pollutants and aggressive species all affect rebar corrosion. Either carbonation or chlorides typically cause steel corrosion in concrete. Carbonation occurs when carbon dioxide in the atmosphere combines with calcium within the concrete. This indicates that the pH of the medium is falling, and the steel rebar is corroding. When chlorides pass through concrete to steel, corrosion rates skyrocket. Consideration must be given to concrete moisture. Owing to its excellent resistance, dry concrete has a low steel corrosion rate, whereas extremely wet concrete has a low rate owing to delayed O 2 transfer to steel surfaces. This paper examines rebar corrosion causes and mechanisms and describes corrosion evaluation and mitigation methods.
KEYWORDs : Reinforced concrete (RC), Steel Rebar, Carbonation Corrosion, Chloride Corrosion, Corrosion Monitoring
AUTHORs : Akib Jabed, Md Mahamud Hasan Tusher † , Md. Shahidul Islam Shuvo, and Alisan Imam

Page : 265 - 272 DOWNLOAD
원전 고온 1차수 환경에서 응력부식균열의 실시간 마이크로 스케일 관찰 방법 개발
The aim of this study was to develop a new in-situ observation method and instrument in micro-scale to investigate the mechanism of stress corrosion cracking (SCC) initiation of Ni-base alloys in a high temperature water environment of pressurized water reactors (PWRs). A laser confocal microscope (LCM), an autoclave with diamond window view port, and a slow strain-rate tester with primary water circulation loop system were components of the instrument. Diamond window, one of the core components of the instrument, was selected based on its optical, chemical, and mechanical properties. LCM was used to observe the specimen in micro-scale, considering the experimental condition of a high-temperature primary water environment. Using in-situ method and instrument, it is possible to observe oxidation and deformation of specimen surface in micro-scale through the diamond window in a high-temperature primary water in real-time. The in-situ method and instrument developed in this work can be utilized to investigate effects of various factors on SCC initiation in a high-temperature water environment.
KEYWORDs : Alloy 600, In-situ observation, Laser confocal microscope, Primary water environment, Stress corrosion cracking
AUTHORs : 신정호 · 이종연 · 김성우†

Page : 257 - 164 DOWNLOAD
플라즈마 전해 산화처리된 Ti-6Al-4V합금의 표면특성에 미치는 울라스토나이트 코팅효과
Ti-6Al-4V alloys are mainly used as dental materials due to their excellent biocompatibility, corrosion resistance, and chemical stability. However, they have a low bioactivity with bioinertness in the body. Therefore, they could not directly bond with human bone. To improve their applications, their bone bonding ability and bone formation capacity should be improved. Thus, the objective of this study was to improve the bioinert surface of titanium alloy substrate to show bioactive characteristics by performing surface modification using wollastonite powder. Commercial bioactive wollastonite powder was successfully deposited onto Ti-6Al-4V alloy using a room temperature spray process. It was found that wollastonite-coated layer showed homogeneous microstructure and uniform thickness. Corrosion resistance of Ti-6Al-4V alloy was also improved by plasma electrolytic oxidation treatment. Its wettability and bioactivity were also greatly increased by wollastonite coating. Results of this study indicate that both plasma electrolytic oxidation treatment and wollastonite coating by room temperature spray process could be used to improve surface bioactivity of Ti-6Al-4V alloy substrate.
KEYWORDs : Biocompatibility, Corrosion resistance, Wollastonite coatings, Plasma electrolytic oxidation, Room temperature spray process
AUTHORs : 고재은 · 이종국† · 최한철†

Page : 252 - 256 DOWNLOAD
모사 슬러리 용액에서 정전류 분극을 활용한 고크롬 주철 부식 시험
The galvanostatic polarization technique was used to accelerate corrosion in high chromium cast iron (HCCI) immersed in a simulated slurry solution of 0.1 mol dm -3 H2SO4, 0.05 mol dm -3HCl, and 10 wt% SiC. The HCCI contained 27 wt% of Cr and 2.8 wt% of C,and its microstructure mainly comprised austenitic and carbide phases. A two-electrode system using a dense carbon rod and the HCCI sample was employed for the galvanostatic polarization by applying an anodic current for 24 hours. The corrosion rate increased upon applying the anodic current, but the increase was not significant, particularly for current densities higher than 10 µAcm-2. Following polarization, the corrosion morphology revealed that the anodic current accelerated surface corrosion in the HCCI; however while the depth of the corroded area increased, the increase was not substantial. The propagation behavior of the anodic current and its impact on corrosion were further discussed.
KEYWORDs : High chromium cast iron, Corrosion, Acidic solution, Galvanostat
AUTHORs : 바산자프 오취개럴 · 이준섭† · 이예진 · 오준석 · 이재현

Page : 242 - 251 DOWNLOAD
고분자전해질 연료전지 분리판용 304 스테인리스 강재의 유기습식및 건식코팅에 따른 내식성 비교연구
The electrochemical corrosion behaviors of 304 stainless steels (STSs) with various coatings (organic coating and dry coating) were examined, and their applicability as bipolar plates in polymer electrolyte membrane fuel cells (PEMFCs) was validated. The results showed that the organic-coated samples had a significant decrease in anodic and cathodic current density compared to the uncoated sample. However, an increase in carbon black content in the organic coating or additional heat treatment at 700o C resulted in a decrease in corrosion resistance. In addition, improvements in corrosion resistance achieved by adding TiO 2 powder to the organic coating were found to be limited. In contrast, dry coating with TiC and CrC exhibited higher corrosion potential, significantly lower current density, and reduced contact resistance compared to the organic coatings. Notably, the TiC-coated sample showed a comparatively lower current density and more stable behavior than the CrC-coated sample. Based on a series of experimental results, a thin TiC coating without defects is proposed as a promising surface treatment strategy for STS bipolar plates in PEMFC.
KEYWORDs : Bipolar plates, Stainless steel, Corrosion, Organic coating, PVD
AUTHORs : 김용현 · 박진성 · 김성진†

Page : 232 - 241 DOWNLOAD
수소연료전지 자동차의 수소밸브용 알루미늄 합금의 수소취화에 의한 기계적 특성에 미치는 CrN과 TiN 코팅의 영향
The mechanical properties of the hydrogen valve responsible for supplying and blocking hydrogen gas in a hydrogen fuel cell electric vehicle (FCEV) were researched. Mechanical properties by hydrogen embrittlement were investigated by coating chromium nitride (CrN) and titanium nitride (TiN) on aluminum alloy by arc ion plating method. The coating layer was deposited to a thickness of about 2 µm, and a slow strain rate test (SSRT) was conducted after hydrogen embrittlement to determine the hydrogen embrittlement resistance of the CrN and TiN coating layers. The CrN-coated specimen presented little decrease in mechanical properties until 12 hours of hydrogen charging due to its excellent resistance to hydrogen permeation. However, both the CrN and TiN-coated specimens exhibited deterioration in mechanical properties due to the peeling of the coating layer after 24 hours of hydrogen charging. The specimens coated at 350oC presented a significant decrease in ultimate tensile strength due to abnormal grain growth.
KEYWORDs : Hydrogen embrittlement, Aluminum alloy, CrN, TiN, Arc ion plating
AUTHORs : 허호성 · 신동호 · 김성종†

Page : 221 - 231 DOWNLOAD
알루미늄 합금의 수소취화 방지를 위한 경질양극산화 및 플라즈마이온질화의 영향
Interest in aluminum alloys for the hydrogen valves of fuel cell electric vehicles (FCEVs) is growing due to the reduction in fuel efficiency by the high weight. However, when an aluminum alloy is used, deterioration in mechanical characteristics caused by hydrogen embrittlement and wear is regarded as a problem. In this investigation, the aluminum alloy used to prevent hydrogen embrittlement was subjected to surface treatments by performing hard anodizing and plasma ion nitriding processes. The hard anodized Al alloy exhibited brittleness in which the mechanical characteristics rapidly deteriorated due to porosity and defects of surface, resulting in a decrease in the ultimate tensile strength and modulus of toughness by 15.58 and 42.51%, respectively, as the hydrogen charging time increased from 0 to 96 hours. In contrast, no distinct nitriding layer in the plasma ion-nitrided Al alloy was observed due to oxide film formation and processing conditions. However, compared to 0 and 96 hours of hydrogen charging time, the ultimate tensile strength and modulus of toughness decreased by 7.54 and 13.32%, respectively, presenting excellent resistance to hydrogen embrittlement.
KEYWORDs : Hydrogen embrittlement, Aluminum alloy, Hard anodizing, Plasma ion nitiridng, Tensile test
AUTHORs : 신동호 · 김성종†

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