• Title, Summary, Keyword: Anodic polarization

Search Result 244, Processing Time 0.039 seconds

A Study on the Corrosion of Al-Alloy Propeller Used for a Coasting Vessel (연안 선박용 Al합금 프로펠러의 부식에 관한 연구)

  • LIM, Uh-Joh;PARK, Hee-Ok;YUN, Byoung-Du
    • Journal of Fisheries and Marine Sciences Education
    • /
    • v.15 no.2
    • /
    • pp.176-183
    • /
    • 2003
  • Recently, with the tendency of lightening, high-strength and high-speed in the marine industries such as marine structures, ships and propellers, it is rapidly enlarged the use of the aluminium alloy. Therefore, there occurs much interest in the study on corrosion characteristics of aluminium alloy. This paper was studied on the corrosion characteristics of Al-Mg alloy propeller used for a coasting vessel. Under the various pH of marine environment, the corrosion test of Al-Mg alloy was carried out. And thus polarization resistance, corrosion potential, and current density behavior of Al-Mg alloy and galvanic corrosion behavior of Al-brass and Al-Mg alloy coupled Al 5086 and SS 400 for hull were investigated. The main results are as following: 1. The corrosion potential of Al-brass propeller is more nobel than materials for hull, but that of Al-Mg alloy propeller is low or similar to materials for hull. Therefore, the galvanic corrosion of hull due to Al-Mg propeller don't occur. 2. The polarization resistance of Al-Mg alloy in sea water of pH 4 is highest, and corrosion current density of Al-Mg propeller is the most controlled. 3. As pH value decreases, potential showed Evans polarization diagram approaches cathodic potential. The corrosion current density of Al-Mg alloy is controlled to anodic reaction rate, therefore, the corrosion reaction of Al-Mg alloy is anodic control.

An Evaluation of Degraded Damage for Superaustenitic Stainless Steel by Electrochemical Polarization Technique (전기화학기법에 의한 슈퍼 오스테나이트 스테인리스강의 열화손상 평가)

  • Kwon, Il-Hyun;Lee, Song-In;Baek, Seung-Se;Lee, Jong-Gi;Iino, Y.;Yu, Hyo-Sun
    • Proceedings of the KSME Conference
    • /
    • /
    • pp.143-148
    • /
    • 2001
  • This research was undertaken to clarify effects of thermal aging on electrochemical and mechanical properties of superaustenitic stainless steel. The steel was artificially aged at $300{\sim}650^{\circ}C$ for $240{\sim}10,000hrs$. and investigated at $-196{\sim}650^{\circ}C$ using small punch(SP) test. Also, the change in electrochemical properties caused by effects of thermal aging was investigated using electrochemical anodic polarization test in a KOH electrolyte. Carbides and ${\eta}-phase(Fe_2Mo)$ precipitated in the grain bounderies seem to deteriorate the mechanical properties by decreasing cohesive strength in the grain bounderies and promote the current density observed in electrochemical polarization curves. The electrochemical and mechanical properties of superaustenitic stainless steel was drastically decreased in the specimen aged at $650^{\circ}C$.

  • PDF

Improvement of Corrosion Resistance for Copper Tube by Electrochemical Passivation (전기화학적 부동태화에 의한 동관의 내식성 개선 연구)

  • Min, Sung-Ki;Kim, Kyung-Tae;Hwang, Woon-Suk
    • Corrosion Science and Technology
    • /
    • v.10 no.4
    • /
    • pp.125-130
    • /
    • 2011
  • This study was performed to improve the corrosion resistance and the stability of passive film on copper tube by potentiostatic polarization method in synthetic tap water. Formation of passive film was carried out by anodic potentiostatic polarization at various passivation potentials and passivation times in 0.1 M NaOH solution. Stability of passive film and corrosion resistance was evaluated by self-activation time, ${\tau}_0$ from passive state to active state on open-circuit state in 0.1 M NaOH solution. Addition of polyphosphate in NaOH solution prolonged the self-activation time and improved the corrosion resistance, and the addition of 5 ppm polyphosphate was most effective. It was also observed that better corrosion resistance was obtained by potentiostatic polarization at 1.0 V (vs. SCE) than at any other passivation potentials. Passivated copper tube showed perfect corrosion resistance for the immersion test in synthetic tap water showing that the anodic potentiostatic polarization treatment in 0.1 M NaOH with 5 ppm polyphosphate solution would be effective in improving the corrosion resistance and preventing the blue water problem.

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 the Korean Society of Marine Engineering
    • /
    • v.29 no.5
    • /
    • pp.519-525
    • /
    • 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 analysis of the duplex aluminum alloys (듀플렉스 알루미늄 합금의 내식성 분석)

  • Choi, In Kyu;Kim, Si Myeong;Kim, Sang Ho
    • Journal of the Korean institute of surface engineering
    • /
    • v.48 no.5
    • /
    • pp.227-232
    • /
    • 2015
  • Corrosion characteristic of the duplex Al-Mg-Si alloys with low, commercial and high solute contents were studied using an anodic polarization test in 1M NaCl solution at room temperature. Polarization range condition of the experiment were form .0.3V to .1.3V with a 0.2 mV scanning speed. The exchange current density means corrosion rate of the low solute alloy was low as about $16.29{\mu}A/cm^2$, and that of the high solute alloy was high as $84.92{\mu}A/cm^2$. The difference was mainly attributed to the inter-granular precipitates $Mg_2Si$ and Si which could make a galvanic corrosion on the aluminum base. The amount of precipitates was greater in high solute alloy at mainly in grain boundary. While, the extruded alloys had better corrosion resistance than the cast alloy because the silicon precipitates become coarse during the extrusion process.

The Effect on the Wear-Corrosion Behavior of Ductile Cast Iron in the Various pH Environments (구상흑연주철재의 마멸-부식특성에 미치는 pH의 영향)

  • 임우조;박동기
    • Tribology and Lubricants
    • /
    • v.19 no.1
    • /
    • pp.31-35
    • /
    • 2003
  • This paper reports the studies on the wear-corrosion behavior of ductile cast iron in the various pH environments. In the variety of pH solutions, corrosion and wear-corrosion loss of GCD 600 were investigated. Also, the anodic polarization test of GCD 600 using potentiostat/galvanostat was carried out. And rubbed surface of GCD 60 using scanning electron micrographs after immersion and wear-corrosion test was examined in the environment of various pH values. The main results are as following In alkali zone, the wear-corrosion loss of GCD 600 increases, but corrosion loss decreases. The unevenness and crack of wear-corrosion surface in neutral zone becomes duller than that in alkali zone. As the corrosive environment is acidified, wear-corrosion behavior of GCD 600 with passing immersion time becomes sensitive.

Property differences between GTAW and SMAW duplex stainless steel weld metal (이상계 스테인레스 강 용접부의 인성과 내식성 거동)

  • 백광기;김희진;안상곤
    • Journal of Welding and Joining
    • /
    • v.4 no.3
    • /
    • pp.58-71
    • /
    • 1986
  • Mechanical and corrosion property of duplex stainless steel weldments made by the GTAW and SMAW process were studied. Fracture toughness, general and local corrosion resistance of GTAW and SMAW weldments were evaluated in terms of Charpy V notch impact test, anodic polarization diagram, pitting corrosion rate, respectively. SMA weld metal showed much lower impact toughness and higher ductile-brittle transition temperature than GTA weld metal. Fractographic and EDX analysis on fracture surface of SMA weld metal demonstrated the existence of (Si, Ti), oxide in large amounts. Potentiodynamic anodic polarization diagram of GMA weld metal showed much lower passive current density than SMA weld metal in 4% $H_2/SO_4$ solution. And pitting corrosion rate test showed the same tendency. Relating the microstructure, chemistry and property, it can be concluded that GTA weld metal gives better toughness due to lower oxygen content, i.e. lower inclusion content, and better corrosion resistance due to higher Pitting Index(PI) than SMA weld metal.

  • PDF

Corrosion Characteristics of Amorphous Alloy Ribbon ($Fe_{70}Cr_5Si_{10}B_{15}$ and $Co_{70}Cr_5Si_{10}B_{15}$) in Hydrochloric Acid Aqueous Solution

  • Choi, Chil-Nam;Hyo, Kyung-Yang;Yang, Myung-Sun
    • Proceedings of the Korean Environmental Sciences Society Conference
    • /
    • /
    • pp.236-237
    • /
    • 2001
  • In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves with amorphous $Fe_{70}Cr_5Si_{10}B_{15}$ and $Co_{70}Cr_5Si_{10}B_{15}$ alloy ribbon. The results were particularly examined to identify the influences of corrosion potential including various conditions such as hydrochloric acid, temperature, salt, pH, and oxygen. The optimum conditions were established with variations including temperature, salt, pH, oxygen, corrosion rate, and resistance of corrosion potential. The mass tranfer coefficient(${\alpha}$) value was determined with the Tafel's slope for the anodic dissolution based on the polarization effect with optimum conditions. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity($I_{r}/I_{f}$).

  • PDF

Affecting of Corrosion Potential and Current Density on Variation Polarization Curves with Polyvinylchloride (I)

  • Choi, Chil-Nam;Yang, Hyo-Kyung;Jung, Oh-Jin
    • Environmental Sciences Bulletin of The Korean Environmental Sciences Society
    • /
    • v.2 no.2
    • /
    • pp.91-98
    • /
    • 1998
  • In this study, we carried out the experiments for measuring the variations of corrosion potential and current density for polarization curves with polyvinylchloride. The results exhibited especially the influence affecting the corrosion potential and various conditions (temperature, day, pH, bacteria, and added salt). The second anodic current density peak and the minimum passive current density are designated $I_P/I_0,$ respectively. The value of $I_P/I_O$ is used as a measurement for the extent of degradation of the polyvinylchloride. The potentiodpnamics parameters of the corrosion were obtained using Tafel equation.

  • PDF

Effect for Alloy Addition(Ta, Zr, Sn) on Mechanical Properties and Corrosion Resistance of cp-Ti for Dental Implants (인공치근용 cp-Ti에 첨가원소(Ta, Zr, Sn)가 기계적 특성 및 내식성에 미치는 영향)

  • Park, H.B.
    • The Journal of Korean Academy of Dental Technology
    • /
    • v.21 no.1
    • /
    • pp.43-53
    • /
    • 1999
  • The mechannical properties and corrosion resistance of alloy added commercially pure titanium for dental implants have been investigated. Ti, To-65Zr, Ti-10.1Ta and Ti-17Sn alloys were melthed in arc furnace and the corrosion resistance of Ti alloys was evaluated by anodic polarization test. The microstructure and mechanical properties of Ti alloy were analysed by optical micrograph. hardness tester and instron. In isothermal test, Ti-10.1Ta and Ti-17Sn alloys exhibited the best oxidation resistance below $1100^{\circ}C$. Ti65Zr, Ti-10.1Ta and Ti-17Sn alloys showed better rockwell hardness compared with commercially pure. Ti As the result of the anodic polarization test in 5%HCl, it 5%HCl, it was known knows that Ti-65Zr, alloy showed a rapid decrease in current density at higher potenial in comparision with other Ti alloys.

  • PDF