• Title, Summary, Keyword: Polarization resistance

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An Electrochemical Evaluation on the Corrosion Resistance of Heavy Anticorrosive Paint (중방식도료의 내식성에 관한 전기화학적 평가)

  • Sung Ho-Jin;Kim Jin-Kyung;Lee Myung-Hoon;Kim Ki-Joon;Moon Kyung-Man
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.5
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    • pp.519-525
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    • 2005
  • An electrochemical evaluation on the corrosion resistance for heavy anticorrosive paint(DFT:25um) was carried out for 5 kinds of heavy anticorrosive paints such as high solid epoxy(HE), solvent free epoxy(SE). tar epoxy(TE), phenol epoxy(PE). and ceramic epoxy(CE). Corrosion current densities obtained by Tafel extrapolation method from anodic and cathodic polarization curves didn't correspond with the values obtained by AC impedance measurement, however, the values of polarization resistance obtained from the cyclic voltammogram showed a good tendency corresponding well with the values of AC impedance measurement. Futhermore there was a good correlation against the corrosion resistance evaluation between passivity current density of the anodic polarization curve and diffusion limiting current density of the cathodic polarization curve. And corrosion resistance increased with corrosion potential shifting to noble direction. From the results discussed above. HE and CE had a relatively good corrosion resistance than other heavy anticorrosive paints.

Corrosion Resistance of the Roll Formed Steel Bolts with the Various Types of Coating Methods (1) (다양한 코팅 방법에 따른 전조한 강 볼트의 내부식성 (1))

  • Mamatov, S.;Hamrakulov, B.;Son, Y.H.;Kim, I.
    • Transactions of Materials Processing
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    • v.28 no.2
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    • pp.71-76
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    • 2019
  • Corrosion resistance is one of the essential properties required in steel bolts. The various types of coatings are used to improve the corrosion resistance of steel bolts. But, roll formed, subsequently Zn alloy electrodeposited and top coated steel bolt easily takes place the white storage stain or white rust under high humidity condition. To investigate the corrosion resistance of roll formed and subsequently the various types of coated steel bolts, their polarization curves were measured by potentio-dynamic tester in this study. Based on the measured polarization curves, the more times of chromate and top coating on roll formed steel bolt, the higher corrosion resistance was shown. The roll formed steel bolt, which was Zn-Ni electro-deposited, two times chromated, one time inorganic top coated, one time organic top coated and annealed, showed the best corrosion resistance.

Critical Pitting Temperature of 2205 Duplex Stainless Steels Using Immersion and Electrochemical Polarization Test Methods (침지시험법 및 전기화학적 분극법에 의한 2205 이상 스테인리스강의 임계공식온도 측정 비교)

  • Shin Jae-Ho;Lee Jae-Bong
    • Journal of the Korean institute of surface engineering
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    • v.39 no.1
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    • pp.18-24
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    • 2006
  • Although stainless steels have the excellent corrosion resistance by passive film, they are susceptible to pitting corrosion in the environment containing halogen elements such as chloride ions. The resistance to pitting corrosion can be evaluated by measuring the critical pitting temperature (CPT). CPT values can be obtained using immersion, potentiodynamic and potentiostatic polarization test methods. Results on duplex 2205 stainless steels showed that CPT values were measured as $50^{\circ}C,\;55^{\circ}C\;and\;61^{\circ}C$, respectively for immersion, potentiodynamic and potentiostatic polarization test methods, depending upon the different test methods, even though the difference between CPT values are not much.

Anodic Polarization Characteristics in Ti-20%Zr(-5%Cr) Alloys for Dental Castings (치과주조용 Ti-20%Zr(-5%Cr)합금의 양극분극특성)

  • Jung, Jong-Hyun;Han, Sok-Yoon
    • Journal of Technologic Dentistry
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    • v.26 no.1
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    • pp.41-48
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    • 2004
  • Ti-20%Zr(-5%Cr) alloys not containing harmful Al and V were newly designed in order to reveal their possibility for dental casting and melted in an arc melting and casting furnace under Ar atmosphere. The corrosion resistance was studied by anodic polarization test. From the observation of anodic polarization behavior, it was found that the corrosion resistance was markedly increased by the addition of Cr. The corrosion resistance of Ti-20%Zr-5%Cr alloy was superior to that in Ti-6%Al-4%V alloy but almost similar to that in CP Ti using in market place today.

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Intepretation of Faradaic Impedance for Corrosion Monitoring

  • Itagaki, M.;Taya, A.;Imamura, M.;Saruwatari, R.;Watanabe, K.
    • Corrosion Science and Technology
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    • v.3 no.1
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    • pp.1-5
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    • 2004
  • A polarization resistance is generally used to estimate the corrosion rate in the corrosion monitoring by an electrochemical impedance method. When the Faradaic impedance has a time constant due to the reaction intermediate, the electrochemical impedance describes more than one loop on the complex plane. For example, the electrochemical impedance of iron in acidic solution shows capacitive and inductive loops on the complex plane. In this case, the charge transfer resistance and the polarization resistance are determined at middle and low frequency ranges, respectively. Which should be selected for corrosion resistance in corrosion monitoring, the charge transfer resistance or the polarization resistance'? In the present paper, the above-mentioned question is examined theoretically and experimentally.

An Electrochemical Evaluation on the Corrosion Resistance of a Al Alloy (주조용 Al합금의 내식성에 관한 전기화학적 평가)

  • Youn Dae-Hyun;Lee Myung-Hoon;Kim Ki-Joon;Moon Kyung-Man
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.5
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    • pp.495-501
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    • 2005
  • Al is a active metal that owes its resistance to a thin, protective, barrier oxide surface layer, which is stable in air and neutral aqueous solution. Thus Al alloys are widely used in architectural trim. cold & hot-water storage vessels and piping. However Al and most of its alloy may corrode with some forms such as pitting corrosion, intergranular corrosion and galvanic corrosion in the case of exposure to various industrial and marine atmosphere. Therefore a correct evaluation of corrosion resistance for their Al and Al alloys may be more important in a economical point of view. In this study. a relative evaluation of corrosion resistance for three kinds of Al alloys such as ALDC2, ALDC3, and ALDC8 series was carried out with electrochemical method. There is a tendency that corrosion potential is shifted to positive or negative direction by alloying components regardless of corrosion resistance. Moreover the data of corrosion properties obtained from cathodic Polarization curve, cyclic voltammogram and AC. DC impedance respectively showed a good correspondence each other against the corrosion resistance but variation of corrosion potential. passivity current density of anodic polarization curve and corrosion current density by Tafel extrapolation and Stern-Geary method didn't correspond with not only each other but also considerably the data of corrosion properties discussed above. Therefore it is suggested that an optimum electrochemical evaluation for corrosion resistance of Al alloy is to calculate the diffusion limiting current density of cathodic polarization curve, impedance of AC or DC and polarization resistance of cyclic voltammogram.

The Study on the Corrosion Characteristics of Cr Plating in Marine Environment (해양환경 중에서 Cr도금의 부식 특성에 관한 연구)

  • 임우조;곽남인;윤병두
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.39 no.3
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    • pp.211-217
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    • 2003
  • Recently, with rapid development in marine and shipbuilding industries such as marine structures, ships and chemical plants for ship, there occurs much interest in the study on corrosion characteristics played an important role in mechanical design. This paper was studies on the corrosion characteristics of chromium plating in the marine environment. Under the various specific resistance, the electrochemical polarization test of chromium plating was carried out. And thus corrosion potential, polarization resistance, corrosion current density, control efficiency of corrosion and polarization control behavior of chromium plating are investigated. The main results are as the followed : 1. The polarization resistance of Cr plating and Ni become higher than that of base metal, also and these material become low with decrease of the specific resistance. 2. As the specific resistance decreases, the corrosion current density of Cr and Ni plating is lower than that of base metal. 3. The corrosion reaction of Cr plating, Ni plating and base metal vs. specific resistance is cathodic control.

Corrosion Resistance of the Roll Formed Steel Bolts with the Various Types of Coating Methods (2) (다양한 코팅 방법에 따른 전조한 강 볼트의 내부식성 (2))

  • Mamatov, S.;Hamrakulov, B.;Son, Y.H.;Kim, I.
    • Transactions of Materials Processing
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    • v.28 no.2
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    • pp.77-82
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    • 2019
  • Corrosion occurs well on surface of roll formed and Zn alloy subsequently electro-deposited on steel bolt under wet condition. In this study, variations in corrosion resistance were investigated through the measurement of polarization curves on steel bolts which were roll formed and subsequently coated with various types of coating methods. According to the measured polarization curve, Ni-P electroless deposits on roll formed steel increased the resistance to corrosion. The corrosion resistance of Zn alloy powder coated steel bolt was found to be better than that of Zn-Ni electro-deposited sample.

A Study on the Mechanical Properties and Corrosion Resistance of GCD40 by Plasma Nitriding (플라즈마 질화처리한 GCD40의 기계적성질 및 내식성에 관한 연구)

  • Kim, M.K.;Jung, B.H.;Kim, S.S.
    • Journal of Power System Engineering
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    • v.6 no.1
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    • pp.74-81
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    • 2002
  • The characteristics of corrosion resistance for the surface of ductile cast iron(GCD40) by plasma nitriding process have been studied in terms of electrochemical polarization behaviors including corrosion potential($E_{corr}$), anodic polarization trends, polarization resistance($R_p$), and also have been studied microstructures, hardness and specific wear of nitrided layer Nitrided layer showed an enhanced hardness values in all the plasma nitriding condition investigated. In the result of wear test, specific wear of nitrided specimens were much decreased than that of non-treated specimens. In the results of XRD, ${\gamma}'phase\;and\;{\varepsilon}$ phase were detected in nitrided surface. And it was found that ${\varepsilon}$ phase was decreased and ${\gamma}'phase$ was increased respectively, as the nitriding time became longer. In the test of corrosion resistance, natural potentials in all the nitrided specimens were towards noble directions than in the case of non-treated specimens. The measurement of electrode potentials revealed that corrosion resistivity of plasma nitrided specimens were higher than in the case of the non-treated specimens.

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Effect of Co Dopant on the (La, Sr)$MnO_3$ Cathode for Solid Oxide Fuel Cell (고체산화물 연료전지용 (La, Sr)$MnO_3$ 양극에 대한 Co 첨가효과)

  • 김재동;김구대;이기태
    • Journal of the Korean Ceramic Society
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    • v.37 no.6
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    • pp.612-616
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    • 2000
  • The effect of Co dopant on the (La, Sr)MnO3 cathode was investigated. La2Zr2O7 and SrZrO3 were formed as the reaction products between YSZ and LSMC. The reactivity of LSMC with YSZ increased with increasing Co content. However, the cathodic polarization resistance decreased with increasing Co doping. Therefore, doping Co at Mn site in the (La, Sr)MnO3 cathode was effective on controlling the polarization resistance of the cathode. The polarization property of LSMC-YSZ composite(60 wt%: 40 wt%) cathode was better than that of LSMC single cathode.

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