• Title/Summary/Keyword: Layered Corrosion

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Detection of Second-Layer Corrosion in Aging Aircraft

  • Kim, Noh-Yu;Yang, Seun-Yong
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.6
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    • pp.591-602
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    • 2009
  • The Compton backscatter technique has been applied to lap-joint in aircraft structure in order to determine mass loss due to exfoliative corrosion of the aluminum alloy sheet skin. The mass loss of each layer has been estimated from Compton backscatter A-scan including the aluminum sheet, the corrosion layer, and the sealant. A Compton backscattering imaging system has been also developed to obtain a cross-sectional profile of corroded lap-splices of aging aircraft using a specially designed slit-type camera. The camera is to focus on a small scattering volume inside the material from which the backscattered photons are collected by a collimated scintillator detector for interpretation of material characteristics. The cross section of the layered structure is scanned by moving the scattering volume through the thickness direction of the specimen. The theoretical model of the Compton scattering based on Boltzmann transport theory is presented for quantitative characterization of exfoliative corrosion through deconvolution procedure using a nonlinear least-square error minimization method. It produces practical information such as location and width of planar corrosion in layered structures of aircraft, which generally cannot be detected by conventional NDE techniques such as the ultrasonic method.

A Study on NDT Techniques for Evaluation of Corrosion in Multi-layered Conductive Structures of Urban Railroad Car of the paper (도시철도차량의 다층 구조물 부식 측정을 위한 비파괴 기법 연구)

  • Lee, Chan-Woo;Chung, Jung-Duk;Song, Sung-Jin
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.2691-2696
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    • 2011
  • THE CARBODY AND BOGIE FRAME OF AN URBAN RAILWAY VEHICLE CONSIST OF MULTI-LAYERED WELDING STRUCTURE. IN KOREA ENDURANCE LIMIT OF AN URBAN RAILWAY VEHICLE IS STSTED IN THE RULE OF MANAGING URBAN RAILWAY VEHICLE UNDER THE LAW OF URBAN RAILWAY. IN KOREA AN URBAN RAILWAY VEHICLE IS DESIGNED AND MADE TO KEEP ITS QUALITY OVER 25 YEARS. WHEN THE RAILWAY VEHICLE BECOMES 25 YEARS OLD, CORROSION OF CARBODY AND UNDER FRAME OF A RAILWAY VEHICLE IS EVALUATED ACCORDING TO THE NON-DESTRUCTIVE TESTING. IT CAN BE USED AS LONG AS 40 YEARS. IT IS STATED IN THE ARTICLE 4 'THE METHOD AND STANDARDS OF PRECISE DIAGNOSIS' UNDER THE RULE OF MANAGING RAILWAY VEHICLE IN KOREA. SO, IN THIS STUDY, WE HAVE INVESTIGATED PERFORMANCE OF PULSED EDDY CURRENT TESTING METHOD BY MEASURING THICKNESS VARIATION OF FABRICATE OF CARBODY AND UNDER FRAME FOR URBAN RAILROAD CAR. AND THEM, THE PROCESS OF EVALUATING REMAINING LIFE ACCORDING TO TESTING OF CORROSION AMOUNT IS INTRODUCED.

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Ignition and flame propagation in hydrogen-air layers from a geological nuclear waste repository: A preliminary study

  • Ryu, Je Ir;Woo, Seung Min;Lee, Manseok;Yoon, Hyun Chul
    • Nuclear Engineering and Technology
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    • v.54 no.1
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    • pp.130-137
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    • 2022
  • In the geological repository of radioactive nuclear waste, anaerobic corrosion can generate hydrogen, and may conservatively lead to the production of hydrogen-air layer. The accumulated hydrogen may cause a hazardous flame propagation resulting from any potential ignition sources. This study numerically investigates the processes of ignition and flame propagation in the layered mixture. Simple geometry was chosen to represent the geological repository, and reactive flow simulations were performed with different ignition power, energy, and locations. The simulation results revealed the effects of power and energy of ignition source, which were also analyzed theoretically. The mechanism of layered flame propagation was suggested, which includes three stages: propagation into the hydrogen area, downward propagation due to the product gas, and horizontal propagation along the top wall. To investigate the effect of the ignition source location, simulations with eight different positions were performed, and the boundary of hazardous ignition area was identified. The simulation results were also explained through scaling analysis. This study evaluates the potential risk of the accumulated hydrogen in geological repository, and illustrates the layered flame propagation in related ignition scenarios.

Galvanic Corrosion Behavior of Copper Canister

  • Minsoo Lee;Junhyuk Jang;Jin Seop Kim
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.22 no.1
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    • pp.55-66
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    • 2024
  • In this study, we investigated the suppression of the corrosion of cast iron in a copper-cast iron double-layered canister under local corrosion of the copper layer. The cold spray coating technique was used to insert metals with lower galvanic activity than that of copper, such as silver, nickel, and titanium, between the copper and cast iron layers. Electrochemically accelerated corrosion tests were performed on the galvanic specimens in KURT groundwater at a voltage of 1.0 V for a week. The results revealed that copper corrosion was evident in all galvanic specimens of Cu-Ag, Cu-Ni, and Cu-Ti. By contrast, the copper was barely corroded in the Cu-Fe specimens. Therefore, it was concluded that if an inactive galvanic metal is applied to the areas where local corrosion is concerned, such as welding parts, the disposal canister can overcome local or non-uniform corrosion of the copper canister for long periods.

High Temperature SO2-gas Corrosion of Fe-18%Cr-10%Ni Steels for Coal-fired Power Plant (화력발전소용 Fe-18%Cr-10%Ni 강의 고온 SO2 가스 부식)

  • Lee, Dong-Bok
    • Journal of Surface Science and Engineering
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    • v.40 no.5
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    • pp.219-224
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    • 2007
  • The corrosion characteristics of Fe-18Cr-10Ni steels were studied between $600^{\circ}C$ and $1000^{\circ}C$ in Ar+(0.2, 1)%$SG_2$ gas for up to 300 hr in order to employ Fe-18Cr-10Ni steels in the coal-fired power plants. The corrosion resistance of Fe-18Cr-10Ni steels was good due mainly to the high amount of Cr, which formed $Cr_2O_3$ from the initial corrosion stage. Fe in the steels corroded to mainly $Fe_2O_3$ and $Fe_3O_4$. Ni was not susceptible to corrosion under the current corrosion condition. Relatively thin, single-layered scales formed.

The Investigation of the Plasma Sprayed Coatings for the Application of OG Cooling Tube in Steel Making Plant

  • Kim, HyungJun;Kwon, YoungGak
    • Corrosion Science and Technology
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    • v.4 no.1
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    • pp.23-28
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    • 2005
  • Several plasma-sprayed ceramic coatings with two- and three-layers were characterized and tested for the application of cooling tube coatings of oxygen convert gas recovery system (OG cooling system) in the steel making plant. Thermal cycling tests using a torch heating with compressed air cooling were carried out and characterized before and after the tests. The effects of metallic bond coat as well as ceramic top coat were also studied. Possible failure mechanisms with low carbon steel substrate were assessed in term of microstructure, porosity, bond strength, thermal expansion coefficient, and the phase transformation. Finally, the results of field tests at the OG cooling system are presented and discussed their microstructural degradation. Test results have shown that three-layered coatings perform better than two-layered coatings.

Dissolution of Mo/Al Bilayers in Phosphoric Acid

  • Kim, In-Sung;Chon, Seung-Whan;Kim, Ky-Sub;Jeon, Il-Cheol
    • Bulletin of the Korean Chemical Society
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    • v.24 no.11
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    • pp.1613-1617
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    • 2003
  • In the phosphoric acid based etchant, the dissolution rates of Mo films were measured by microgravimetry and the corrosion potentials of Mo and Al were estimated by Tafel plot method with various concentrations of nitric acid. Dissolution rate of Mo increased with the nitric acid concentration and reached a limiting value at high concentration of nitric acid in ambient condition. Corrosion potentials of Mo and Al shifted to positive direction and the difference between potentials of both metals was about 1,100 mV and 1,200 mV with 1% and above 4% of $HNO_3$, respectively. For a Mo/Al bilayers, the dissolution rate inversion is the main reason for good taper angle in shower etching process. Taper angles are observed by scanning electron microscope (SEM) after wet etching process for Mo/Al layered films with different concentrations of $HNO_3$. In the etch side profile, it was found that Al corroded faster than Mo below 4% of $HNO_3$ in dip etching process, however, Mo corroded faster above 4%. Trend for variation of taper angle of etched side of Mo/Al layered film can be explained by considering the effect corrosion rates of both metals with various concentrations of $HNO_3$.

Fabrication of Chromium-based Double Layered Deposit (크롬계 이중도금층 제조 및 특성평가)

  • Park, Sang-Eon;Kim, Dong-Su;Kim, Man;Jang, Do-Yeon;Gwon, Sik-Cheol
    • 연구논문집
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    • s.31
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    • pp.127-133
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    • 2001
  • In chromium electrodeposition, crack is inevitably accompanied by chromium layer. Behavior of crack formation and crack density were different from the plating conditions such as current density, temperature, waveform of applied current and so on. And cracks have an influence on the corrosion resistance of chromium deposit, because corrosion occurs through the network of cracks between deposit and substrate. Therefore, many researches have been achieved in order to remove the cracks in chromium deposit. Formation of double layers, Cr/Cr and Ni/Cr were investigated to increase corrosion resistance of chromium deposit in this study. As pretreatment prior to outer chromium coating, acid pickling and current control method were examined. Cracks in cross-section of each sample were observed with SEM and CASS(Copper modified acetic acid salt spray) test was performed to evaluate corrosion resistance. It was found that corrosion resistance of Cr/Cr and Ni/Cr double layers were superior to Cr or Ni single layer from the results of CASS test.

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Corrosion Protection from Inhibitors and Inhibitor Combinations Delivered by Synthetic Ion Exchange Compound Pigments in Organic Coatings

  • Chrisanti, S.;Ralston, K.A.;Buchheit, R.G.
    • Corrosion Science and Technology
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    • v.7 no.4
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    • pp.212-218
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    • 2008
  • Inorganic ion exchange compounds (IECs) including hydrotalcites and bentonite clays are a well known classes of layered mixed metal hydroxides or silicates that demonstrate ion exchange properties. These compounds have a range of applications from water purification to catalyst supports. The use of synthetic versions of these compounds as environmentally friendly additives to paints for storage and release of inhibitors is a new and emerging application. In this paper, the general concept of storage and release of inhibiting ions from IEC-based particulate pigments added to organic coatings is presented. The unique aspects of the IEC structure and the ion exchange phenomenon that form the basis of the storage and release characteristic are illustrated in two examples comprising an anion exchanging hydrotalcite compound and a cation exchanging bentonite compound. Examples of the levels of corrosion protection imparted by use of these types of pigments in organic coatings applied to aluminum alloy substrates is shown. How corrosion inhibition translates to corrosion protection during accelerated exposure testing by organic coatings containing these compounds is also presented.

Effect of Loading Path on the Hydroformability of a Three-layered Tube for Fabrication of a Hollow Part (중공품 성형시 삼중관의 액압성형성에 미치는 압력경로의 영향)

  • Han, S.W.;Kim, S.Y.;Joo, B.D.;Moon, Y.H.
    • Transactions of Materials Processing
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    • v.22 no.1
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    • pp.17-22
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    • 2013
  • Tube hydroforming is a technology that utilizes hydraulic pressure to form a tube into desired shapes inside die cavities. Due to its advantages, such as weight reduction, increased strength, improved quality, and reduced tooling cost, single-layered tube hydroforming is widely used in industry. However in some special applications, it is necessary to produce multi-layered tubular components which have corrosion resistance, thermal resistance, conductivity, and abrasion resistance. In this study, a hollow forming process to fabricate a part from multi-layered tubes for structural purposes is proposed. To accomplish a successful hydroforming process, an analytical model that predicts optimal load path for various parameters such as tube material properties, thickness of tubes, diameter of holes and the number of holes was developed. Tubular hydroforming experiments to fabricate a hollow part were performed and the optimal loading path developed by the analytical model was successfully verified. The results show that the proposed hydroforming process can effectively produce hollow parts with multi-layered tube without defects such as wrinkling or fracture.