• Title, Summary, Keyword: Polarization resistance

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THE ELECTROCHEMICAL STUDY ON CORROSION RESISTANCE OF VARIOUS DENIAL MAGNETIC ATTACHMENTS (수종 치과용 자석유지장치의 부식저항성에 대한 전기화학적 연구)

  • Sohn Byoung-Sup;Chang Ik-Tae;Heo Seong-Joo;Keak Jai-Young
    • The Journal of Korean Academy of Prosthodontics
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    • v.39 no.4
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    • pp.336-350
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    • 2001
  • The purpose of this study was to investigate corrosion tendency and to compare corrosion resistance of three dental magnetic attachments and its keeper alloy by coercive, electrochemical method. By using petentiodynamic polarization technique, magnetic elements and its keeper alloy of Magfit EX600 system(MF, MFK), Dyna ES regular system(DN, DNK) and Shiner SR magnet system(SR, SRK) were corroded electrochemically in 0.9% NaCl electrolytic solution. Open-circuit potential and anodic polarization curve was measured with Potentiostat(model 273 EG&E) and polarization curve was created by current density per square area following scanning of increased series of voltage in the rate of 1.0mV per second. Before and after electrochemical corrosion, the surface roughness test was done. Thereafter the change of mean surface roughness value(Ra) and mean peak value(Rt) of surface roughness was compared one another. In order to observe the corroded surface of each specimen, metallurgical light microscopic(${\times}37.5$) and scanning electron microscopic view(SEM ${\times}100$) was taken and compared one another. Conclusion is followings. 1. All of six covering metal of dental magnetic attachments and its keeper alloy were corroded in various degree after electrochemical corrosion. 2. The corrosion resistance of which used in this experiment is the following in high order; DNK, MFK, DN, MF, SRK and SR. 3. Especially Shiner magnet system and its keeper alloy were more severely corroded after electrochemical corrosion and the change of Ra Rt value were more increased than others. 4 Metallurgical and scanning electron microscopic view showed the pitting corrosion tendency of all experimental alloy but DNK and SR. 5. Covering metal of magnet was more corroded than its keeper alloy.

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The Study on the Wear-Corrosion Behavior of Ductile Cast Iron in the Acidic Environment (산성환경 중에서 구상흑연주철재의 마멸-부식거동에 관한 연구)

  • Lim, Uh-Joh;Park, Dong-Gi;Yun, Byoung-Du
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.96-102
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    • 2002
  • This paper was studied on the wear-corrosion behavior of ductile cast iron in the acidic environment. In the dry atmosphere and variety of pH solution, wear-corrosion characteristics and friction coefficient of GCD 60 with various sliding speed and distance were investigated. And electrochemical polarization test of GCD 60 was examined in the environment of various pH value. The main results are as following : In the dry atmosphere, boundary friction appears below nearly 5 $kg_{f}$ of contact load, and it is considered that solid friction occurs over nearly 5 $kg_{f}$ of contact load. As pH value becomes low, wear-corrosion loss in the aqueous solution increases. As the corrosion environment is acidified, corrosion potential of GCD 60 becomes noble, polarization resistance becomes low, and corrosion current density increases.

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The Anodicc PolarizationBehavior of Fe-Cr-Ni-W alloy in 1N HCI Solution (1N 염산 용액에서 Fe-Cr-Ni-W 합금의 양분극 거동에 관한 연구)

  • 윤재돈;강성군
    • Journal of the Korean institute of surface engineering
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    • v.21 no.4
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    • pp.176-182
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    • 1988
  • Effects of Cr, Ni and W on the anodic polarization behavior were investigated for Fe-Cr-Ni-W alloys in deaerated 1N HCI solution. Surface films formed on the polarization were analysed using AES, SEM and EDAX. A higerconcentration of tungten was found in the surface oxide film compared to the matrix. It played an importanet role on incresing the stability of the passive film. The presence of an adequate amount of Cr was essential to increase the pitting resistance of the alloys in acid chloride media. Under 12 wt%cr,alloys containing 6wt%W did not exhidit any passivity at all. The main role of Ni was to control the microstructure rather than to modify the corrosion resistance. In 23 cr-14Ni-^W alloy, the duplex microstructure of ferrite($\delta$-phase) in an austenic matrix was developed. The reson why proferred pitting appeared in austenite and ferrite/austenite interface was that ferrite had more amount of Cr and W than austenite.

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Impedance Properties of LSMC-YSZ Composite Cathode (LSMC-YSZ Composite 양극의 임피던스 특성)

  • 김재동;김구대;문지웅;김창은;이동아
    • Journal of the Korean Ceramic Society
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    • v.35 no.9
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    • pp.917-922
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    • 1998
  • The polarization characteristics of the cathodes were discussed which were composed YSZ and ${(La_{0.75 }Sr_{0.25 })}_{0.95}Mn_{0.8 }Co_{0.2}O_3$ The three-phase-boundary length increased with the addition of YSN resulting in the minimum po-larization resistance at 60(LSMC) : 40(YSZ) wt% When LSMC-YSZ compoiste cathodes was sintered at $1200^{\circ}C$ minimum polarization resistance was observed and the capacitace increased with increasing sintering tem-perature.

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A Study on the Preparation of Poly(vinyl alcohol) Polarizing Film (폴리비닐알코올 편광필름 제조에 관한 연구)

  • 김삼수;우화령;류원석
    • Textile Coloration and Finishing
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    • v.16 no.4
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    • pp.19-25
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    • 2004
  • Both poly(vinyl alcohol)$(PVA)-I_2$ and PVA-dye polarizing film were prepared using PVA with number-average degree of polymerization of 1,700, 2,300, 2,600. The optical property of used dye in this study closed to the that of iodine. The PVA-dye polarizing film was prepared through the dyeing process. In comparison of the result of the measurement of the heat and humidity resistance of two types polarizing films, it of PVA-dye polarizing film was higher than that of a conventional $PVA-I_2$polarizing film. The transmittance and the polarization efficiency of PVA-dye polarizing film was significantly influenced by dye concentration, dipping time, salt concentration, and temperature of dye bath. The PVA-dye polarizing film exhibited a high polarization efficiency of 99.3% and a good transmittance of 42.4%.

Effect of Drawing Rate on the Corrosion Behavior of Al Alloy Tubes for Automotive Cooling System (인발률에 따른 자동차 냉각 배관용 Al 합금의 부식 특성에 관한 연구)

  • Park, Byung-Joon;Kim, Jung-Gu;Ahn, Seung-Ho;Kwak, Dong-Ho;Sohn, Hyun-Soo
    • Korean Journal of Metals and Materials
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    • v.46 no.8
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    • pp.489-494
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    • 2008
  • The effect of drawing rate on the electrochemical properties of 3003 Al alloys in 5 wt.% NaCl solution was investigated by electrochemical techniques (potentiodynamic polarization test, potentiostatic polarization test, electrochemical impedance spectroscopy (EIS)) and surface analyses (OM, SEM, EDS). Four kinds of automotive pipe materials were prepared (raw material, drawing rate = 5, 10, 15%). As the drawing rate of Al alloy tube increased, the pitting corrosion resistance increased due to the enrichment of Al oxides on the surface.

Effect of Stress on the Polarization Characteristic of Al-brass (Al-황동의 분극특성에 미치는 응력의 영향)

  • Lim, Uh-Joh;Jeong, Hae-Kyoo;Sim, Kyong-Tae
    • Journal of the Korean Society of Safety
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    • v.19 no.2
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    • pp.1-5
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    • 2004
  • Al-brass is the raw material of mnufacturing tubes for heat exchanger of vessel where seawater is used to coolant because it has high level of heat coductivity and excellent mechanical properties and high level of corrosion resistance due to cuprous oxide($Cu_2O$) layer against seawater. However, damage of Al-brass tubes for heat exchanger of vessel is reported that local corrosion such as stress corrosion cracking occurred by synergism effect between mechanical factor and corrosion environment. In this study, to investigate on the effect of stress on the polarization characteristics of Al-brass. At the stress of 0% and 95% yield strength by constant displacement tester, in 3.5% NaCl + 0.1% $NH_4OH$ solution, the polarization tests were carried out. And thus open circuit potential, corrosion current density, anodic polarization, cyclic polarization and dezincification behavior of Al-brass are investigated.

Analysis and Experiment Verification of Heat Generation Factor of High Power 18650 Lithium-ion Cell (고출력 18650 리튬이온 배터리의 발열인자 해석 및 실험적 검증)

  • Kang, Taewoo;Yoo, Kisoo;Kim, Jonghoon
    • The Transactions of the Korean Institute of Power Electronics
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    • v.24 no.5
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    • pp.365-371
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    • 2019
  • This study shows the feasibility of the parameter of the 1st RC parallel equivalent circuit as a factor of the heat generation of lithium-ion cell. The internal resistance of a lithium-ion cell consists of ohmic and polarization resistances. The internal resistances at various SOCs of the lithium-ion cell are obtained via an electrical characteristic test. The internal resistance is inversely obtained through the amount of heat generated during the experiment. By comparing the resistances obtained using the two methods, the summation of ohmic and polarization resistances is identified as the heating factor of lithium-ion battery. Finally, the amounts of heat generated from the 2C, 3C, and 4C-rate discharge experiments and the COMSOL multiphysics simulation using the summation of ohmic and polarization resistances as the heating parameter are compared. The comparison shows the feasibility of the electrical parameters of the 1st RC parallel equivalent circuit as the heating factor.

Electrical Properties of the Lanthanum Ferrite-Based Cathode Materials for Low-Temperature SOFCs (저온 작동형 SOFC Lanthanum Ferrite계 공기극 소재의 전기적 특성)

  • Kang, Ju-Hyun;Choi, Jung-Woon;Shim, Han-Byel;Yoo, Kwang-Soo
    • Journal of the Korean Ceramic Society
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    • v.43 no.3
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    • pp.162-168
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    • 2006
  • The perovskites with nominal compositions $La_{0.8}Sr_{0.2}Fe_{1-x}M_xO_3$ (M=Co, Mn, Ni, x=0.1-0.3) were fabricated by a solid-state reaction method as cathode materials of low-temperature operating Solid Oxide Fuel Cells (SOFCs). X-ray diffraction analysis and microstructure observation for the sintered samples were performed. The ac complex impedance were measured in the temperature range $600-900^{\circ}C$ in air and fitted with a Solatron ZView program. The electrical conductivity and polarization resistance of $La_{0.8}Sr_{0.2}Fe_{1-x}M_xO_3$ (M=Co, Mn, Ni, x=0.1-0.3) were characterized systematically. The porosities of the sintered samples were in the range of 25% to 38%. The polarization resistance of $La_{0.8}Sr_{0.2}Fe_{0.7}M_{0.3}O_3$ was $0.291{\Omega}cm^2\;at\;700^{\circ}C$.

The Effect of Cr from STS Interconnect on the Polarization Resistance of LSCF Cathode (스테인리스 스틸 연결재의 Cr이 LSCF 양극의 분극저항에 미치는 영향)

  • Hwang, Ho-June;Choi, Gyeong-Man
    • Journal of the Korean Ceramic Society
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    • v.44 no.12
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    • pp.715-719
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    • 2007
  • STS444 with or without $La_{0.9}Sr_{0.1}MnO_3$ (LSM)-coating was contacted to $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ (LSCF) cathode on various electrolyte materials and the polarization resistance $(R_p)$ was measured by impedance spectroscopy. By making a symmetric half-cell and contacting only one side of the cathode with the interconnect, the effect of chromium (Cr) poisoning was separated from the aging effects. When the LSCF cathode was contacted with LSM-coated STS (stainless steel), $R_p$ of LSCF was lower than that contacted with the uncoated STS. Impedance patterns measured for the working electrode (W.E.), the counter electrode (C.E.) at $600^{\circ}C$ in air were analyzed. Normalized data of net Cr effect showed that $Ce_{0.9}Gd_{0.1}O_2$ (GDC) electrolyte is more tolerant to the chromium poisoning than $La_{0.9}Sr_{0.1}Ga_{0.8}Mg_{0.2}$ (LSGM) or 8 mol% $Y_2O_3-doped$ $ZrO_2$ (YSZ) electrolytes.