• Title/Summary/Keyword: Surface corrosion

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Corrosion Properties of Carbon-Coated Metallic Bipolar Plate for PEMFC (고분자 전해질 연료전지 금속 분리판 적용을 위한 탄소 박막의 증착과 내식성 평가)

  • Jang, Dong-Su;Lee, Jung-Joong
    • Journal of the Korean institute of surface engineering
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    • v.48 no.3
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    • pp.87-92
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    • 2015
  • Carbon thin films were deposited on STS 316L sheets by inductively coupled plasma enhanced magnetron sputtering with or without substrate bias voltage. Typical Raman spectrum for amorphous diamond-like carbon (DLC) was obtained, and the interfacial contact resistance (ICR) was measured to show its conductive nature. The electrochemical impedance spectroscopy (EIS) was used to investigate the corrosion mechanism of the carbon coating under the polymer electrolyte membrane fuel cell (PEMFC) condition. According to the pore-corrosion mechanism, the electrolyte penetrates the carbon coating through the pores and reacts with the substrate. As the substrate corrosion proceeds, the pore enlargement occurs and the surface area of the substrate exposed to the electrolyte. Applicability of the carbon coating for the PEMFC bipolar plate was evaluated by potentiodynamic polarization experiments. Finally, an adhesion problem was briefly considered.

A Study on Wear Characteristics of Machine Structural Steel by Surface Modification (표면개질에 의한 기계구조용강의 마멸특성에 관한 연구)

  • Park Heung-Sik;Woo Kyu-Sung
    • Tribology and Lubricants
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    • v.22 no.2
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    • pp.73-78
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    • 2006
  • The surface modification of automobile parts is of great technological importance for the improvement of corrosion resistance, wear resistance, fatigue strength and so on. Recently, research on the development of the technology of surface modification substituting 6-balance chrome process has progressively been achieved in automobile parts. Although the innovation technology for the improvement of the corrosion-resisting and wear resistant properties through post oxidation after nitrocarburising process had attracted a great attention. For this, anodically potentiodynamic polarisation testing was carried out to corrosion resistance and friction and wear experiment according to applied load and sliding distance was carried out to evaluate the wear resistance of machine structural steel with nitrocarburising and non-nitrocarburising SM45C. The presumed wear volume was calculated with the image processing far evaluation of wear resistance of two materials. The results show that the nitrocarburising had a distinguished corrosion resistance and wear resistance than non-nitrocarburising.

Integrated characterization of the corrosion products of Mg alloy (마그네슘 합금 부식 산화물에 대한 특성 연구)

  • Gwon, Sang-Jun;Heo, Jin-Yeong;Lee, Hong-Gi
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2015.05a
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    • pp.179-180
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    • 2015
  • pure Mg and some Mg alloys are relatively rapidly corroded after operation, resulting in the decrease of mechanical strength and change of local ion concentration. In this study, the corrosion mechanism of biodegradable implant materials was investigated by corrosion tests of the Mg alloy in Hank's solution. Particularly, the crystal structures and chemical bonding state of corrosion reactants was systematically examined.

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An Experimental Investigation of the Effect of Corrosion on Dry Friction Noise (건성마찰 소음에 대한 부식 영향도 실험연구)

  • Baek, Jongsu;Kang, Jaeyoung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.12
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    • pp.1251-1256
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    • 2015
  • This study investigates the friction noise characteristic in relation to the corrosion of metal by using the frictional reciprocating and pin-on-disk system. From the experiments, it is found that the corrosion of metal advances the onset time and increases the magnitude of friction noise. Further, it is observed that the effect of corrosion on friction noise stems from the alteration of tribo-surface during repetitive frictional motion. The alteration of the corrosive contact surface induces a negative friction-velocity slope, by which the corrosion of metal can generate dynamic instability faster than non-corrosion of metal.

Evaluation of Corrosion and the Anti-Cavitation Characteristics of Cu Alloy by Water Cavitation Peening (동합금의 워터캐비테이션피닝에 의한 내구성과 부식특성 평가)

  • Kim, Seong-Jong;Han, Min-Su;Kim, Min-Sung
    • Corrosion Science and Technology
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    • v.11 no.5
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    • pp.184-190
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    • 2012
  • Cu alloy is widely used for marine applications due to its excellent ductility and high resistance for corrosion as wells as cavitation. However, long term exposure of the material to marine environments may result in damages caused by cavitation and corrosion. Water cavitation peening has been introduced in order to improve resistance of Cu alloy to corrosion and cavitation. The technology induces compressive residual stress onto the surface, and thus enhances the fatigue strength and life. In this study, the characteristics of the material were investigated by using water cavitaiton peening technique, and results showed that 2 minutes of water cavitation peening indicated the considerable improvement in hardness. On the other hand, over 10 minutes of water cavitation peening accelerated damages to the surface. In the case of ALBC3, water cavitation peening in the range of 2 to 10 minutes has shown the excellent durability and corrosion resistance while minimizing surface damages.

Effect of Annealing Temperature on the Nodular Corrosion of Zircaloy-4 Alloy (Zircaloy-4 합금의 Nodule형 부식에 미치는 열처리 온도의 영향)

  • 정용환;최종술;임갑순
    • Journal of the Korean institute of surface engineering
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    • v.24 no.1
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    • pp.31-41
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    • 1991
  • The nodular corrosion behavior of Zircaloy-4 alloy was investigated by autoclave test at 50$0^{\circ}C$ under 1500 psi for the specimens quenched into water from $700^{\circ}C$, 80$0^{\circ}C$, 90$0^{\circ}C$, and 105$0^{\circ}C$. It was observed that the corrosion resistance of Zircalloy-4 specimen increased with increase in annealing temperature, and annealing at $\alpha$-region temperatures resulted in nodular corrosion while annealing at the temperature range of $\alpha$+$\beta$ and $\beta$ did not show nodular corrosion. It was also found that the size of nodule formed on the surface of the specimens increased with increase in exposure time in autoclave, but the total number of nodule remained uncha-nged. The corrosion of furnace-cooled specimens progressed mostly in the interior of grains where Fe and Cr alloying elements were largely depleted during the cooling process. However, the grain boundary seemed to act as a barrier to the nodular corrosion. From combining the present results with other works, it is suggested that the nodules nuc-leate in the local region where some of alloying elements are depleted.

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Determination of Chemical Compositions and Oxidation States for Corrosion Products in LiCl Molten Salts

  • Park, Yong-Joon;Pyo, Hyung-Ryul;Kim, Do-Yang;Jee, Kwang-Yong;Kim, Won-Ho
    • Nuclear Engineering and Technology
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    • v.32 no.5
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    • pp.514-520
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    • 2000
  • The mechanism of corrosion behavior has to be understood clearly to select an optimum material for handling molten salts to be used in the oxide reduction process of PWR spent fuel. In this study, the oxidation states of corrosion products on the surface of Inconel 600 and 800H as well as their chemical compositions and structural informations were determined by using XPS, ICP-AES, AAS, EPMA and XRD after the corrosion experiment with lithium molten salts at 75$0^{\circ}C$ for 25 hours. Nickel and oxygen were detected from the corrosion products on the surface of Inconel plates and chromium was found to be dissolved out into lithium molten salts leaving cracks on the surface. The corrosion products were identified as metal oxides such as Fe$_2$O$_3$, Cr$_2$O$_3$, NiO, NiFe$_2$O$_4$and MnO by using XPS and XRD.

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Crevice Corrosion Behavior by Measuring the Potential Inside the Crevice and Repassivation Characteristics of Alloy 600 and Alloy 690 (틈 내 전위측정을 통한 Alloy 600 및 Alloy 690의 틈부식 거동과 재부동태 특성)

  • Oh, Se-Jung;Lee, Jae-Bong
    • Journal of the Korean institute of surface engineering
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    • v.40 no.2
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    • pp.82-90
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    • 2007
  • Crevice corrosion is the accelerated attack occurred in the occluded cell under a crevice on the metal surface. Crevice corrosion behaviors of nickel-based alloys such as Alloy 600 and Alloy 690 were investigated in acidic solution with different chloride ion concentrations. Tests were carried out using the specially designed crevice cell with a very narrow Luggin capillary assembly to measure the potential inside the crevice. It is believed that crevice corrosion in active/passive system like nickel-based alloys has much to do with the properties of passive film and its repassivation characteristics, investigated by the capacitance measurement and by the abrading electrode technique, respectively. An attempt was made to elucidate the relationship between crevice corrosion behaviors, properties of passive film and its repassivation kinetics. Results showed that repassivation rate parameter $n1{\leq}0.6$ and/or $n2{\leq}0.5$ indicated the possible occurrence of crevice corrosion.

Effects of Casting Method and Rolling on the Corrosion Behaviors of Pb Alloys for a Lead Acid Battery (주조 방식 및 압연에 따른 연축전지용 납 합금 기판의 부식 특성)

  • Oh, KkochNim;Lee, Kyu Hyuk;Jang, HeeJin
    • Corrosion Science and Technology
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    • v.20 no.5
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    • pp.315-323
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    • 2021
  • 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 twin-belt 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.

Variation of Corrosion Properties on the Steel Surface by Environmental Changes in Shihwa Lake (시화호 환경 변화에 따른 강재 표면의 부식특성 변화)

  • Park, Jun-Mu;Lee, Seung-Hyo;Woo, Sang-Kyun;Chu, In-Yeop;Lee, Myeong-Hoon
    • Journal of the Korean institute of surface engineering
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    • v.51 no.5
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    • pp.316-324
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    • 2018
  • Harsh seawater environment is subdivided into marine atmosphere, splash zone, tidal zone, submerged zone and bottom of sea depending on the exposed part. Since corrosion rate depends on the conditions of the exposed parts, proper protection and maintenance for each parts are essential for long-term use of steel structures in seawater environment. For steel structures which were installed in Shiwha Lake, a special maintenance system is required to guarantee its long-term durability and safety. As the tidal power plant has recently been operated, the salinity has risen due to the rapid influx of seawater upstream into Sihwa Lake and the corrosion tendency of the structure is variable according to the water level fluctuation. In this study, corrosion properties of steel structures under water level fluctuation was evaluated by corrosion rate measurement, visual inspection and natural potential measurement and their durability and life management were discussed in view of the effect of variation in of seawater level fluctuations in Shihwa Lake.