한국부식방식학회

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Page : 315 - 323 DOWNLOAD
주조 방식 및 압연에 따른 연축전지용 납 합금 기판의 부식 특성
In this study, we examined corrosion behaviors of two types of Pb alloys for a lead acid battery comparatively. One containing 6.6 wt% Sn, 36 mg/kg Bi, and 612.4 mg/kg Ca was prepared by twin-roll continuous casting. The other containing 5.2 wt% Sn, 30.5 mg/kg Ag, and 557 mg/kg Ca was made by twinbelt continuous casting. Potentiodynamic polarization tests were performed to evaluate corrosion resistance. Cyclic voltammetry was done to examine oxidation and reduction reactions occurring on the surface of each alloy in 4.8 M H2SO4 solution. Electrochemical test results implied that the Pb alloy prepared with the twin-belt casting method was less stable than that cast with the twin-roll method. Such results might be due to precipitations formed during the casting process. Rolling did not appear to affect the corrosion behavior of the twin-roll samples with Ag < 10 mg/kg, while it reduced the anodic reaction of Ag on the surface of the twin-belt sample with 30.5 mg/kg Ag.
KEYWORDs : Lead acid battery, Pb alloy, Corrosion, Rolling
AUTHORs : 오꽃님 · 이규혁 · 장희진†

Page : 308 - 314 DOWNLOAD
중성자 조사에 따른 Ni도금피복재에서의 He발생량평가
Neutron dose level at bottom head of a reactor pressure vessel (RPV) was calculated using reactor vessel neutron transport for a Korean nuclear power plant A. At 34 EFPY with a 40-year (2042) design life after plating repair, irradiation fast neutron effect was 6.6x1015 n/cm2. As helium(He) gas can be generated by Ni only at 1/106 level of 5 × 1021 n/cm2, He generation possibility in the Ni plating layer is very little during 40 years of operation (2042, 34 EFPY). Thermal neutrons can significantly affect the generation of He from Ni metal. At 10 years after a repair, He can be generated at a level of about 0.06 appm, a level that can add general welding repair without any consideration. After 40 years of repair, 9.8 appm of He may be generated. Although this is a rather high value, it is within the range of 0.1 to 10 appm when welding repair can be applied. Clad repair by Ni electroplating technology is expected to greatly improve the operation efficiency by improving the safety and shortening the maintenance period of the nuclear power plant.
KEYWORDs : Nuclear power plant, Corrosion of RPV steel, Ni plating, Neutron effect, He generation
AUTHORs : 황성식† · 권준현 · 김동진 · 김성우

Page : 295 - 307 DOWNLOAD
초고강도급 자동차용 강재 내 ε-carbide (Fe2.4C)가 부식 및 수소확산거동에 미치는 영향
Effects of ε-carbide (Fe2.4C) on corrosion and hydrogen diffusion behaviors of ultra-strong steel sheets for automotive application were investigated using a number of experimental and analytical methods. Results of this study showed that the type of iron carbide precipitated during tempering treatments conducted at below A1 temperatures had a significant influence on corrosion kinetics. Compared to a steel sample with cementite (Fe3C), a steel sample with ε-carbide (Fe2.4C) showed higher corrosion resistance during a long-term exposure to a neutral aqueous solution. In addition, the diffusion kinetics of hydrogen atoms formed by electrochemical corrosion reactions in the steel matrix with ε-carbide were slower than the steel matrix with cementite because of a comparatively higher binding energy of hydrogen with ε-carbide. These results suggest that designing steels with fine ε-carbide distributed uniformly throughout the matrix can be an effective technical strategy to ensure high resistance to hydrogen embrittlement induced by aqueous corrosion.
KEYWORDs : Ultra high-strength steel, Tempering, Corrosion, Hydrogen diffusion, Iron carbide
AUTHORs : 박진성 · 윤덕빈 · 성환구 · 김성진†

Page : 289 - 294 DOWNLOAD
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

Page : 281 - 288 DOWNLOAD
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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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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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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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†

Page : 242 - 248 DOWNLOAD
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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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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