• Title, Summary, Keyword: Polarization resistance

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Anodic Polarization Properties of Ti-Zr-Pd Based Alloys for Biomedical Applications (생체용 Ti-Zr-Pd계 합금의 양극분극특성)

  • Jung, Jong-Hyun
    • The Journal of Korean Academy of Dental Technology
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    • v.23 no.1
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    • pp.21-30
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    • 2001
  • For biomedical applications. Ti-X%Zr-Y%Pd(X: $10{\sim}20$, Y:0.2 or 0.4) based alloys not containing harmful Al and V were newly designed, and polarization curves for their alloys were measured at $37^{\circ}C$ in 5% HCl solution in order to understand effects of Zr on the corrosion. From the results of anodic polarization behavior, it was found that the corrosion resistance increased with increasing Zr content. The results show their potential to develope Ti-based alloys for biomedical materials. The Ti-20%Zr-0.2%Pd alloy shows excellent corrosion resistance and was superior to those of the Ti. Ti-6%Al-4%V ELI alloy, Co-30%Cr-6%Mo alloy and STS 316L stainless steel.

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Corrosion Characteristics of Reinforced Steel Bar Emedded in Multiple Mortar Specimen(W/C:0.5) Aged 5 Years in Seawater

  • Moon, Kyung-Man;Takeo, Oki;Won, Jong-Pil;Park, Dong-Hyun;Kim, Yun-Hae
    • International Journal of Ocean System Engineering
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    • v.3 no.1
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    • pp.33-37
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    • 2013
  • Reinforced concrete structures have been increasingly widely used in numerous industrial fields. These structures are often exposed to severely corrosive environments such as seawater, contaminated water, acid rain, and the seashore. Thus, the corrosion problems that occur with the steel bars embedded in concrete are very important from the safety and economic points of view. In this study, the effects of the cover thickness on the corrosion properties of reinforced steel bars embedded in multiple mortar test specimens immersed in seawater for 5 years were investigated using electrochemical methods such as the corrosion potentials, polarization curves, cyclic voltammograms, galvanostat, and potentiostat. The corrosion potentials shifted in the noble direction, and the value of the AC impedance also exhibited a higher value with increasing cover thickness. Furthermore, the polarization resistance increased with increasing cover thickness, which means that the oxide film that is deposited on the surface of a steel bar surrounded by alkali environment exhibits better corrosion resistance because the water, chloride ions and dissolved oxygen have difficulty penerating to the surface of the steel bar with increasing cover thickness. Consequently, it is considered that the corrosion resistance of reinforced steel can be improved by increasing the cover thickness. However, the corrosion resistance values of a steel bar estimated by measuring the corrosion potential, impedance and polarization resistance were not in good agreement with its corrosion resistance obtained by polarization curves.

A Study on the Crevice Corrosion Behavior of Chromium Plating (크롬도금의 틈부식 거동에 관한 연구)

  • 곽남인;임우조
    • Journal of the Korean institute of surface engineering
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    • v.36 no.4
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    • pp.324-328
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    • 2003
  • This study was made on the crevice corrosion behavior of chromium plating in fresh water. Under the various crevice, the electrochemical polarization test of chromium plating was carried out. Results are discussed In terms of corrosion potential, polarization resistance, corrosion current density and cathodic control of chromium plating.

Performance degradation of SOFC caused by increase of polarization resistance for the cathode during long-term test (공기극 분극 저항 증가에 따른 SOFC 단전지 성능 감소에 관한 연구)

  • Park, Kwang-Jin;Bae, Joong-Myeon
    • 한국신재생에너지학회:학술대회논문집
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    • pp.349-352
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    • 2009
  • In this study, the relation between the performance degradation of SOFC single cell and the increase of polarization resistance for the cathode is investigated. $Pr_{0.3}Sr_{0.7}Co_{0.3}Fe_{0.7}O_3$(PSCF3737, $19.4{\times}10^{-6}K^{-1}$) and $Gd_{0.1}Ce_{0.9}O_2$ (CGO91, $12{\times}10^{-6}K^{-1}$) are used as a cathode and an electrolyte, respectively. The polarization resistance of cathode is increased due to the delamination caused by thermal expansion coefficient difference. The voltage drop with 10%/1000h decline rate occurs during long-term, when the interface between the cathode and the electrolyte is delaminated due to TEC difference.

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The Study of Corrosion of Heat Exchanger Tube for Absorption Refrigeration Machine (흡수식냉동기용 열교환기 세관의 부식에 관한 연구)

  • 임우조;정기철;윤병두
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.147-152
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    • 2002
  • This paper was studied on corrosion of heat exchanger tube for absorption refrigeration machine. In the 62 % lithium bromide solution at $60^{\circ}C$, polarization test of Cu, Al-brass, 10 % cupro nickel(90-10 % Cu-Ni) and 30 % cupronickel(70-30 % Cu-Ni) tube was carried out. And polarization behavior, polarization resistance characteristics, open circuit potential, anodic polarization of heat exchanger tube for absorption refrigeration machine were considered. The main results are as following: The open circuit potential of Al-brass tube becomes less noble than that of Cu tube, corrosion current density of that becomes lower than Cu tube. The open circuit potential of cupronickel tube is more noble than that of Cu tube, corrosion current density of that is controlled than Cu tube. The passivation critical current of 30 % Cu-Ni tube is lower than that of 10 % Cu-Ni tube, potential of passive region of that is more wide than 10 % Cu-Ni tube.

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The Study on the Corrosion Characteristics of Al-Alloy Shell for Cooler (알루미늄합금 원통냉각기의 부식 특성에 관한 연구)

  • 임우조;김성진;윤병두
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.39 no.2
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    • pp.152-157
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    • 2003
  • Most Recently, with rapid development in marine industries such as marine structures and ship, there occurs much interest in the study of corrosion characteristics which play an important role in design of cooling water system like heat-exchanger. Especially, as operating environment of fresh cooling water system in vessels is acidified, this system is seriously corroded. In this study, to study on the corrosion characteristics of Al-alloy shell for cooler, the electrochemical polarization test of materials for the marine fresh water cooler such as Al-alloy, Cu and naval brass was carried out in fresh water. And thus the polarization resistance and anodic polarization behavior of Al-alloy, Cu and naval brass are investigated. Also, galvanic corrosion characteristics of Al-alloy coupled with Cu and naval brass is considered. The main results obtained are as follows ; (1) The current density of corrosion is high in order of Al-alloy > naval brass > Cu (2) As anodic potential increases, the corrosion resistance of naval brass is better than that of Cu. (3) The galvanic corrosion of Al-alloy coupled with Cu and naval brass is activated than corrosion of Al-alloy.

Monitoring of Initial Stages of Atmospheric Zinc Corrosion in Simulated Acid Rain Solution under Wet-dry Cyclic Conditions

  • EL-Mahdy, Gamal A.;Kim, Kwang B.
    • Corrosion Science and Technology
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    • v.3 no.6
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    • pp.251-256
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    • 2004
  • Exposure of zinc samples in simulated acid rain solution (SARS) was investigated under a periodic wet-dry conditions using an AC impedance technique. The periodic wet and dry exposure consisted of the immersion of zinc samples in SARS for one hour followed by exposure to 7 hours drying at 60% RH. Phases of the corrosion products were indentified by X-ray diffraction (XRD). The influence of relative humdiity (RH), temperature, and surface inclination on the atmospheric corrosion of zinc is described. The reciprocal of polarization resistance (1/Rp) decreases rapidly during the initial stages then slowly and eventually attains a steady state as exposure time progresses. The average of reciprocal of polarization resistance per cycle, (ARPR) was calculated and found to decrease as number of exposure cycle increases. An increase of temperature enhances the corrsion rate of zinc. The values of ARPR, of a sample inclined at 30 o are lower than those for a sample oriented horizontally. The experiment result shows a pronounced dependence of reciprocal of polarization resistance on RH. Exposure in the presence of carbonate anions gives rise to more protective corrosion products than in nitrate anion solution. The corrosion mechanism during the initial stages of atmospheric zinc corrosion under wet-dry cyclic conditions is suggested.

A Study on the Anti-corrosion Properties of Organic and Inorganic Inhibitor by Electrochemical Evaluation Method in Saturated Aqueous Solution of Calcium Hydroxide (포화 수산화칼슘 수용액 내에서의 무기계 및 유기계 방청제의 전기화학적 방식 특성평가)

  • Kim, Soo-Young;Ryu, Hwa-Sung;Kim, Sung-Kil;Lee, Han-Seung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.4
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    • pp.66-74
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    • 2013
  • In this study, corrosion potential ($E_{corr}$), corrosion rate, and polarization resistance were measured aimed at inorganic inhibitors (passive film type) and organic inhibitors (absorption type). The experiment was conducted using potentiostat for the variable molar ratio and chloride ion concentration of the components of inhibitors in an aqueous solution of saturated calcium hydroxide targeting corrosion. As a result, it was possible to ensure an anticorrosive performance of at least a 1.2 molar ratio of inorganic inhibitors. Also, the organic inhibitors ensured the prevention of the anticorrosive performance of at least about a 0.3 molar ratio. It also showed the tendency that between polarization resistance and corrosion rate, Ecorr and corrosion rate is inversely proportional to the linear. Conversely, the tendency between polarization resistance and Ecorr is proportional to the linear. Also, a distinct difference in organic and inorganic inhibitors' relationship to Ecorr, corrosion rate, and polarization resistance was not shown.

Study on the Damage Behavior of 304 Stainless Steel for Gas Boiler with Specific Resistance (비저항에 따른 가스보일러용 304스테인리스강재의 손상거동에 관한 연구)

  • Yun, Byoung-Du;Lim, Uh-Joh;Jeong, Ki-Cheol
    • Journal of the Korean Institute of Gas
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    • v.9 no.4
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    • pp.6-10
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    • 2005
  • This paper was studied on the damage behavior of stainless steel (STS 304) for gas boiler with specific resistance. The electrochemical polarization test of STS304 for gas boiler was carried out. And the anodic polarization and damage aspect, such as pitting corrosion, was considered. With being low specific resistance, the passive current density of STS 304 increases, passive region and pitting potential is low. Also, the patting aspect of STS304 In specific resistance $74{\Omega}{\cdot}m$ water little appears, the pitting number increases and the damage behavior, such as pitting aspect, gradually grow bigger with being low specific resistance.

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Effects of the Polarization Resistance on Cyclic Voltammograms for an Electrochemical-Chemical Reaction

  • Chang, Byoung-Yong
    • Journal of Electrochemical Science and Technology
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    • v.6 no.4
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    • pp.146-151
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    • 2015
  • Here I report an electrochemical simulation work that compares voltammetric current and resistance of a complex electrochemical reaction over a potential scan. For this work, the finite element method is employed which are frequently used for voltammetry but rarely for impedance spectroscopy. Specifically, this method is used for simulation of a complex reaction where a heterogeneous faradaic reaction is followed by a homogeneous chemical reaction. By tracing the current and its polarization resistance, I learn that their relationship can be explained in terms of rate constants of charge transfer and chemical change. An unexpected observation is that even though the resistance is increased by the rate of the following chemical reaction, the current can be increased due to the potential shift of the resistance made by the proceeding faradaic reaction. This report envisions a possibility of the FEM-based resistance simulation to be applied to understand a complex electrochemical reaction. Until now, resistance simulations are mostly based on equivalent circuits or complete mathematical equations and have limitations to find proper models. However, this method is based on the first-principles, and is expected to be complementary to the other simulation methods.