• Title, Summary, Keyword: Anodic polarization

Search Result 244, Processing Time 0.044 seconds

Effect of the Mixed Electrolyte on the Film Growth and Corrosion Characteristics of Anodized Al 6061 Alloy (Al 6061 합금 양극산화피막의 성장과 부식특성에 미치는 혼합 전해용액의 영향)

  • Ryu, Han-Woong;Kim, Yong-Hwan;Chung, Uoo-Chang;Chung, Won-Sub
    • Korean Journal of Materials Research
    • /
    • v.17 no.5
    • /
    • pp.244-249
    • /
    • 2007
  • The properties of anodized films on aluminum 6061 alloy in single electrolyte of sulfuric acid and mixed electrolyte of sulfuric-boric acid and sulfuric-boric-nitric acid have been studied. Polarization tests in NaC solution were used to investigate the corrosion performance. Characteristics of film formation and surface morphology were examined by optical microscopy, FE-SEM and EDS. The results obtained have indicated that oxide films growth have been promoted by nitric acid and anodized films in mixed electrolyte have superior corrosion resistance. In case of anodic films formed in mixed electrolyte, some grooves and numerous crazings were also observed at the surface.

An Nondestructive Evaluation of Degraded Damage for Superaustenitic Stainless Steel (슈퍼 오스테나이트 스테인리스강의 열화손상에 대한 비파괴적 평가)

  • Kwon, Il-Hyun;Baek, Seung-Se;Iino, Y.;Yu, Hyo-Sun
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.26 no.7
    • /
    • pp.1332-1339
    • /
    • 2002
  • This research was undertaken to clarify effects of thermal aging on electrochemical and mechanical properties of superaustenitic stainless steel and to detect the material degradation nondestructively. The steel was artificially aged at $300{\sim}650^{\circ}C$ for $240{\sim}10,000h$ and the mechanical properties were investigated at $-196{\sim}650^{\circ}C$ using small punch(SP) test. Also, the change in electrochemical properties caused by effects of thermal aging on superaustenitic stainless steel was investigated using electrochemical anodic polarization test in a KOH electrolyte. Carbides and ${\eta}-phase(Fe_2Mo)$ precipitated in the grain boundaries seem to deteriorate the mechanical properties by decreasing cohesive strength in the grain boundaries and to promote the current density observed in electrochemical polarization curves, The electrochemical and mechanical properties of superaustenitic stainless steel decreased significantly in the specimen aged at $650^{\circ}C$ corresponding to the sensitization temperature for conventional austenitic stainless steels.

Study on the Cavitation Damage of Cupronickel(70/30) Tube for Gas Absorption Refrigeration Machine

  • Lim, Uh-Joh;Jeong, Ki-Cheol;Yun, Byoung-Du
    • Journal of the Korean Society of Marine Engineering
    • /
    • v.28 no.2
    • /
    • pp.332-337
    • /
    • 2004
  • The use of gas absorption refrigeration machine has considerably increased because of the shortage of the electric power in the summer and the regulation of freon refrigerant. Gas absorption refrigeration machine consists of a condenser, a heat exchanger. supplying pipes, a radiator etc, This system is likely to be corroded by acid. dissolved oxygen and gases, Cavitation erosion-corrosion by flow velocity of cooling water may happen in absorption refrigeration machine. In these cases. erosion and corrosion occur simultaneously. Then, it makes a serious damage with synergy effect. Therefore, this paper was studied on the cavitation damage of cupronickel(70/30) tube for gas absorption refrigeration machine, In the $30^{\circ}C$ tap water, linear polarization test and anodic polarization test were carried out for copper(C1220T-OL) and cupronickel(70/30) tube. Also, cavitation erosion-corrosion behavior of cupronickel (70/30) tube was considered, The main results are as following: (1) In the linear test, the corrosion current density of cupronickel(70/30) is higher than that of copper. (2) The erosion-corrosion rate of cupronickel(70/30) displayed later tendency than that of copper by vibratory cavitation in cooling water. (3) In cooling water, the progress mechanism of erosion-corrosion rate of copper and cupronickel(70/30) follows a pattern of incubation, acceleration, attenuation and a steady state period.

Evaluation of Corrosion Resistance of Ti-Zr-Nb-Pd Based Alloys for Biomedical applications by electron Theory (전자론에 의한 생체용 Ti-Zr-Nb-Pd계 합금의 내식성 평가)

  • Jung, Jong-Hyun;Sun, Gum-Ju
    • The Journal of Korean Academy of Dental Technology
    • /
    • v.26 no.1
    • /
    • pp.35-40
    • /
    • 2004
  • In order to understand alloying effects on the corrosion resistance of Ti-(10$\sim$20)%Zr-(2$\sim$8%)Nb-0.2%Pd alloys, Polarization curves were measured at 5%HCI solution. The results were interpreted in terms of two parameters obtained by the molecular orbital calculation ; one is the bond order($B_{\circ}$) and the other is the metal d-orbital level($M_{d}$). $B_{\circ}$ is a measure of the strength of covalent bonds between titanium and alloying elements. $M_{d}$ is correlative with the electronegativity of elements. It was found that increasing of Zr and Nb with higher $B_{\circ}$ values showed a lower critical anodic current density in the polarization curve and hence higher corrosion resistance. On the other hand, increasing of Zr and Nb with higher $M_{d}$ values showed a higher corrosion resistance.

  • PDF

Anodic Dissolution Property and Structure of Passive Films on Equiatomic TiNi Intermetallic Compound

  • Lee, Jeong-Ja;Yang, Won-Seog;Hwang, Woon-Suk
    • Corrosion Science and Technology
    • /
    • v.6 no.6
    • /
    • pp.311-315
    • /
    • 2007
  • The anodic polarization behavior of equiatomic TiNi shape memory alloy with pure titanium as a reference material was investigated by means of open circuit potential measurement and potentiodynamic polarization technique. And the structure of passive films on TiNi intermetallic compounds was also conducted using AES and ESCA. While the dissolved Ni(II) ion did not affect the dissolution rate and passivation of TiNi alloy, the dissolved Ti(III) ion was oxidated to Ti(IV) ion on passivated TiNi surface at passivation potential. It has also been found that the Ti(IV) ion increases the steady state potential, and passivates TiNi alloy at a limited concentration of Ti(IV) ion. The analysis by AES showed that passive film of TiNi alloy was composed of titanium oxide and nickel oxide, and the content of titanium was three times higher than that of nickel in outer side of passive film. According to the ESCA analysis, the passive film was composed of $TiO_2$ and NiO. It seems reasonable to suppose that NiO could act as unstabilizer to the oxide film and could be dissolved preferentially. Therefore, nickel oxide contained in the passive film may promote the dissolution of the film, and it could be explained the reason of higher pitting susceptibility of TiNi alloy than pure Ti.

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
    • /
    • v.9 no.4
    • /
    • pp.6-10
    • /
    • 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.

  • PDF

Effect of Nitrogen Ion Implantation on Corrosion Resistance of Biocompatible Ti Implant (질소이온의 주입이 생체안전성 티타늄임플란트의 내식성에 미치는 영향)

  • 최종운;손선희
    • Journal of the Korean Society of Safety
    • /
    • v.14 no.3
    • /
    • pp.134-139
    • /
    • 1999
  • In this study, PSII(plasma source ion implantation) was used to improve the biocompatibility of bone-anchored Ti implant. According to potentiodynamic anodic polarization test in deaerated Hank's solution, open circuit potential of ion implanted specimens were increased compare to that of unimplanted specimen ; besides, passive current density and critical anodic current density of ion implanted specimens were lower than unimplanted specimen.

  • PDF

Degradation Damage Evaluation of High Temperature Structural Components by Electrochemical Anodic Polarization Test (전기화학적 양극분극시험에 의한 고온 설비부재의 열화손상 평가)

  • Yu, Ho-Seon;Song, Mun-Sang;Song, Gi-Uk;Ryu, Dae-Yeong
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.24 no.6
    • /
    • pp.1398-1407
    • /
    • 2000
  • The structural steels of power plant show the decrease of mechanical properties due to degradation such as temper embrittlement, creep damage and softening during long-term operation at high temper ature. The typical causes of material degradation damage are the creation and coarsening of carbides(M23C6, M6C) and the segregation of impurities(P, Sb and Sn) to grain boundary. It is also well known that material degradation induces the cleavage fracture and increases the ductile-brittle transition temperature of steels. So, it is very important to evaluate degradation damage to secure the reliable and efficient service condition and to prevent brittle failure in service. However, it would not be appropriate to sample a large test piece from in-service components. Therefore, it is necessary to develop a couple of new approaches to the non-destructive estimation technique which may be applicable to assessing the material degradation of the components with not to influence their essential strength. The purpose of this study is to propose and establish a new electrochemical technique for non-destructive evaluation of material degradation damage for Cr-Mo steels which is widely used in the high temperature structural components. And the electrochemical anodic polarization test results are compared with those of semi-nondestructive SP test.

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
    • /
    • /
    • pp.147-152
    • /
    • 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.

  • PDF

Visualization of Ion Transport and pH Change in Ion Concentration Polarization (농도 분극 현상에서의 이온의 흐름과 pH 변화의 가시화)

  • Ko, Sung-Hee;Kang, Kwan-Hyoung
    • Journal of the Korean Society of Visualization
    • /
    • v.8 no.4
    • /
    • pp.38-42
    • /
    • 2010
  • Ion concentration polarization is an electrokinetic phenomenon which occurs in membrane systems, such as in an electrodialysis and fuel-cell system. But the phenomenon is not fully understood because hydrodynamics, electrokinetics and electrochemistry are coupled with each other. Here, we report that there occurs a change of pH value of buffer solution in concentration polarization phenomenon. To visualize the change of pH, the litmus solution which is one of the pH indicators was used. It is conjectured that the pH of solution changes because hydrogen ions were concentrated in cathodic side and hydroxide ions were concentrated in anodic side. We anticipate that this work may contribute to the fundamental understanding on the ion concentration polarization phenomenon.