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Page : 196 - 203
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- 자동차용 핫스탬핑 AlSi 도금중 Mg 첨가효과
- To improve corrosion resistance and reduce the hydrogen uptake of 22MnB5, up to 5% Mg was added to the AlSi coating of 22MnB5. After hot-stamping and electrocoating were done on the metallic-coated specimen, the surface characteristics of the steel, hydrogen uptake content, and corrosion resistance were examined by transmittance electron microscopy, thermal desorption spectrometry, cyclic corrosion testing, and electrochemical impedance spectroscopy. Mg was investigated as MgO on the surface layer after hotstamping while it existed as Mg2Si before hot-stamping. The total hydrogen content of 22MnB5 was decreased along with the Mg content. However, there was no difference at 0.2 wt% or more. When a small amount of Mg was added, the coating corrosion resistance was decreased, but when it was added at around 1.0 wt%, the greatest corrosion resistance increase was seen. However, when 3 wt% or more was added excessively, the corrosion resistance was decreased. MgO on the surface was considered to suppress H uptake by the AlSi melting solution and increase the barrier effect of the coating.
- KEYWORDs : Corrosion, AlSi coating, Hot stamping, Hydrogen Embrittlement
- AUTHORs : 양원석† · 이재민 · 김창규 · 안승호 · Homero Castaneda
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Page : 204 - 209
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- 판형 열교환기 전열판의 부식 파손 분석
- Corrosion failure analysis of the flow plate, which is one of the accessories of the plate heat exchanger in a district heating system, was performed. The flow plate is made of 316 stainless steel, and water at different temperatures in the flow plate exchanges heat in a non-contact manner. The flow plate samples in which water mixing issues occurred were collected. Corrosion-induced pits, oxides, and contaminants were observed at locations where two plates are regularly in contact. The EDS analysis of the surface oxides and contaminants revealed that they were composed of carbon, silicon, and magnesium, which came from chemical adhesives. The IC/ICP analyses showed that the concentration of chloride ions was 30 ~ 40 ppm, which was not sufficient to cause corrosion of stainless steel. In the crevice, a local decrease in dissolved oxygen occurs along with an increase in chloride ions, thus forming an acidic environment. These environments destroyed the passive film of stainless steel, resulting in pits. Moreover, contaminants formed a narrower gap between the two metal plates and inhibited the diffusion of ions, thereby accelerating crevice corrosion.
- KEYWORDs : Plate heat exchanger, Flow plate, Crevice corrosion, Adhesive
- AUTHORs : 송민지 · 최가현 · 채호병 · 김우철 · 김희산 · 김정구 · 이수열†
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Page : 210 - 229
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- 원자로 내부구조물 균열개시 민감도에 미치는 영향인자 고찰
- To safely operate domestic nuclear power plants approaching the end of their design life, the material degradationvmanagement strategy of the components is important. Among studies conducted to improve the soundness of nuclear reactor components, research methods for understanding the degradation of reactor internals and preparing management strategies were surveyed. Since the IGSCC (Intergranular Stress Corrosion Cracking) initiation and propagation process is associated with metal dissolution at the crack tip, crack initiation sensitivity was decreased in the hydrogenated water with decreased crack sensitivity but occurrence of small surface cracks increased. A stress of 50 to 55% of the yield strength of the irradiated materials was required to cause IASCC (Irradiation Assisted Stress Corrosion Cracking) failure at the end of the reactor operating life. In the threshold-stress analysis, IASCC cracks were not expected to occur until the end of life at a stress of less than 62% of the investigated yield strength, and the IASCC critical dose was determined to be 4 dpa (Displacement Per Atom). The stainless steel surface oxide was composed of an internal Cr-rich spinel oxide and an external Fe and Ni-rich oxide, regardless of the dose and applied strain level.
- KEYWORDs : Nuclear power plant, Stainless steels, IASCC initiation, Dissolved hydrogen, Threshold fluence
- AUTHORs : 황성식† · 최민재 · 김성우 · 김동진
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Page : 231 - 242
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- Electrochemical Frequency Modulation: Solution Resistance and Double Layer Capacitance Considerations
- The objective of this study was to evaluate total current under steady-state conditions for a material undergoing corrosion using the electrochemical frequency modulation (EFM) technique, taking into account the presence of solution resistance and double layer capacitance. The analysis involving linearization of the Tafel curve allowed for the estimation of corrosion parameters. Results showed that the output signal was dependent on fundamental frequencies and their multiples. In addition, the output signal almost manifested itself at frequencies that were sums of fundamental frequencies of the applied sinusoidal signal. The harmonics calculated showed a significant shift from the principal frequency of input signals. The investigation involved the influence of corrosion current and anode-to-cathode Tafel slope ratio on faradaic and non-faradaic currents (including the average and RMS). The model presented showed both qualitative and quantitative improvements over the previously developed EFM technique that ignored the influence of solution resistance and the double layer capacitance while assuming the applied DC potential corresponded to the corrosion potential of the corroding material.
- KEYWORDs : Modulation, Corrosion, EFM, Frequency
- AUTHORs : Shashi Lalvani†, Sifat Ullah, and Lei Kerr
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Page : 242 - 248
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- Failure Investigation of Fire-Side Water-Wall Tube Boiler
- Unforeseen failures of boilers in power plants may affect the continuation of electricity generation. Main failures in boilers are influenced by the tube material, tube position, boiler service temperature and pressure, and chemical composition of the feed water and coal. This investigation was intended to find answers on the causes and mechanism of failure of the fire-side boiler water-wall tubes, due to perforation and corrosion. The tube conformed to the material requirements in terms of its chemical composition and hardness. Microscopic examination showed ferrite and pearlite indicating no changes in its microstructure due to the temperature variation. SEM test showed a single layer and homogenous film density particularly on the area far from perforation. However, layers of corrosion product were formed on the nearby perforation area. EDX showed that there were Na, Ca, S, and O elements on the failed surface. XRD indicated the presence of Fe2O3 oxide. The failure mechanism was identified as a result of significant localized wall thinning of the boiler water wall-tube due to oxidation.
- KEYWORDs : Failure, Hardness, Wall thinning, Perforation, Oxidation
- AUTHORs : M. C. Fatah†, D. Agustiadi, and A. W. Pramono
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Page : 249 - 255
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- Fabrication of a Porous Copper Current Collector Using a Facile Chemical Etching to Alleviate Degradation of a Silicon-Dominant Li-ion Battery Anode
- In this work, we proposed a facile method to fabricate the three-dimensional porous copper current collector
(3D Cu CC) for a Si-dominant anode in a Li-ion battery (LiB). The 3D Cu CC was prepared by combining
chemical etching and thermal reduction from a planar copper foil. It had a porous layer employing
micro-sized Cu balls with a large surface area. In particular, it had strengthened attachment of Si-dominant
active material on the CC compared to a planar 2D copper foil. Moreover, the increased contact area
between a Si-dominant active material and the 3D Cu could minimize contact loss of active materials from
a CC. As a result of a battery test, Si-dominant active materials on 3D Cu showed higher cyclic performance
and rate-capability than those on a conventional planar copper foil. Specifically, the Si electrode
employing 3D Cu exhibited an areal capacity of 0.9 mAh cm-2 at the 300th cycles (@ 1.0 mA cm-2), which
was 5.6 times higher than that on the 2D copper foil (0.16 mAh cm-2). - KEYWORDs : Lithium-ion battery, Copper current collector, Silicon-dominant anode, Porous structure, degradation
- AUTHORs : Hongsuk Choi, Subin Kim, Hayong Song, Seokho Suh, Hyeong-Jin Kim†, and KwangSup Eom†
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Page : 256 - 265
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- 내식성 향상을 위한 기능성 타이타늄 표면 개질
- Titanium is applied in various industries due to its valuable properties and abundant reserves. Generally, if a highly uniform oxide structure and a high-density oxide film is formed on the surface through anodization treatment, the utility value such as color appearance and corrosion inhibition efficiency is further increased. The objective of this study was to determine improvement of water-repellent property by controlling titanium oxide parameters such as pore size and inter-pore distance to improve corrosion resistance. Oxide film structures of different shapes were prepared by controlling the anodization processing time and voltage. These oxide structures were then analyzed using a Field Emission Scanning Electron Microscope (FE-SEM). Afterwards, a Self-Assembled Monolayer (SAM) coating was performed for the oxide structure. The contact angle was measured to determine the relationship between the shape of the oxide film and the water-repellency. The smaller the solid fraction of the surface, the higher the waterrepellent
effect. The surface with excellent hydrophobic properties showed improved corrosion resistance. Such water-repellent surface has various applications. It is not only useful for corrosion prevention, but also useful for self-cleaning. In addition, a hydrophobic titanium may open up a new world of biomaterials to remove bacteria from the surface. - KEYWORDs : Titanium Oxide Nanostructure, Anodization, Water-Repellent Property, Anti-Corrosion
- AUTHORs : 박영주 · 정찬영†
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Page : 266 - 280
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- 순환동전위 분극실험을 이용한 스테인리스강의 그린데스용액에서 전기화학적 특성에 미치는 온도의 영향
- Since 2020, the International Maritime Organization (IMO) has updated regulations on the sulfur content to be less than 0.5% in exhaust gas emitted from ships. Accordingly, the exhaust gas post-treatment device for ships, which is SOx/NOx reduction technology, was introduced. However, the exhaust gas post-treatment device is suffering corrosion because of the harsh corrosive environment formed by sulfate and chlorine oxide through the desulfurization process. In this investigation, cyclic potentiodynamic polarization (CPDP) experiment for UNS S31603 and UNS N08367 was performed in a green death solution that simulates the environment of a desulfurization device. The corrosion rate of UNS S31603 at the highest temperature was about 3 times higher than that of UNS N83067. Also, electron microscope scan revealed corrosion type UNS N83067 presents intergranular corrosion tendency. On the other hand, UNS S31603 was observed as general corrosion. The α values of UNS N08367 at 30 oC and 60 oC were higher than those of UNS S31603, thus UNS N08367 is considered to have a higher local damage tendency. Whereas, since the α value of UNS S31603 at 90 oC is larger than that of UNS N08367, UNS S31603 is considered to have a higher local damage trend.
- KEYWORDs : UNS S31603, UNS N08367, Green death solution, Temperature, Cyclic potentiodynamic polarization
- AUTHORs : 황현규 · 김성종†
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Page : 281 - 288
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- 오스테나이트계 스테인리스강과 니켈합금의 해수 농도 변화에 따른 전기화학적 부식 손상 특성
- Due to advancement of the industry, operation of a device in a harsh environment is increasing. Especially, the marine environment contains Cl- ions which causes localized corrosion such as pitting and crevice corrosion of stainless steel and various metals. In this study, electrochemical corrosion behaviors of austenitic stainless steel (STS 316L) and nickel alloy (Inconel 600) with different seawater concentrations (fresh water, seawater, mixed water) were investigated. The STS 316L and Inconel 600 were etched in 10% oxalic acid and composed of an austenitic phase. Results of Tafel analysis in seawater showed that STS 316L and Inconel 600 presented the highest corrosion current densities of 7.75 × 10-4 mA/cm2 and 1.11 × 10-4 mA/cm2 and the most negative pitting potentials of 0.94 V and 1.06 V, respectively. The maximum damage depths and surface damage ratio by pitting corrosion increased with chloride concentration. The STS 316L had higher PREN than Inconel 600. However, the surface damage and weight loss of Inconel 600 were superior to STS 316L. It was difficult to compare the pitting resistance of STS 316L based on Fe and Inconel 600 based on Ni with PREN simply.
- KEYWORDs : STS 316L, Inconel 600, Seawater concentration, Electrochemical corrosion, PREN
- AUTHORs : 허호성 · 김성종†
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Page : 289 - 294
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- 반도체 패키징용 금-코팅된 은 와이어의 부식특성
- In this study, after measuring polarization characteristics of 97.3 wt% Ag, Au-Coated 97.3 wt% Ag (ACA) and 100 wt% Au wires in 1 wt% H2SO4 and 1 wt% HCl electrolytes at 25 oC, corrosion rate and corrosion characteristics were comparatively analyzed. Comparing corrosion potential (ECORR) values in sulfuric acid solution, ACA wire had more than six times higher ECORR value than Au wire. Thus, it seems possible to use a broad applied voltage range of bonding wire for semiconductor packaging which ACA wire could be substituted for the Au wire. However, since the ECORR value of ACA wire was three times lower than that of the Au wire in a hydrochloric acid solution, it was judged that the use range of the applied voltage and current of the bonding wire should be considered. In hydrochloric acid solution, 97.3 wt% Ag wire showed the highest corrosion rate, while ACA and Au showed similar corrosion rates. Additionally, in the case of sulfuric acid solution, all three types showed lower corrosion rates than those under the hydrochloric acid solution environment. The corrosion rate was higher in the order of 97.3 wt% Ag > ACA > 100 wt% Au wires.
- KEYWORDs : Semiconductor Packaging, Corrosion, Bonding wire, Au-Coated Ag wire (ACA), Au wire
- AUTHORs : 홍원식† · 김미송 · 김상엽 · 전성민 · 문정탁 · 김영식
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