• Journal of Advanced Marine Engineering and Technology
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• 제29권6호
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• pp.654-661
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• 2005

Copper is a well known alloying element that is used to improve the resistance to general corrosion of stainless steel And also Cu cation have the anti-fouling effect to inhibit adhesion of the marine algae and shellfish to the surface of heat exchanger cooling pipe or outside wall of the ship, Therefore there are some anti-fouling methods such as anti-fouling Paint mixed with copper oxide or MGPS(Marine Growth Preventing System) by using Cu cation dissolved to the sea wather solution. Cu cation can be dissolved spontaneously by galvanic current due to Potential difference between Cu and cooling pipe of heat exchanger with Ti material, which may be one of the anti-fouling designs. In this study the effect of annealing heat treatment to galvanic current and Polarization behavior was investigated with a electrochemical points of view such as measurement of corrosion Potential, anodic polarization curve. cyclic voltammetric curve, galvanic current etc The grain size of the surface in annealed at $700^{\circ}C$ was the smallest than that of other annealing temperatures. and also the corrosion Potential showed more positive potential than other annealing temperatures. The galvanic current between Ti and Cu with annealed at $700^{\circ}C$ was the largest value in the case of static condition. However its value in the case of flow condition was the smallest than the other temperatures. Therefore in order to increase anti-fouling effect by Cu cation, the optimum annealing temperature in static condition of sea water is $700^{\circ}C$, however non- heat treated specimen in the case of flow condition may be desirable.

• Corrosion Science and Technology
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• 제5권6호
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• pp.218-221
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• 2006

Influence of microstructure on the corrosion property of Mg-Al-Zn alloy was investigated using potentiodynamic polarization experiments, galvanic coupling experiments, and scanning electron microscopy in sodium chloride solutions. Pitting was the most common form of attack in chloride solution, and filiform corrosion was also occurred in AZ91D-T4 alloy. On the contrary, filiform attack in the bulk matrix was predominant corrosion form in AZ91D-T6 alloy, and the number and size of pit were decreased than those of AZ91D-T4 alloy. Galvanic coupling effect between $Mg_{17}Al_{12}$ and matrix was existed, but the propagation of galvanic corrosion was localized only near the $Mg_{17}Al_{12}$ phase in AZ91D-6T alloy. The corrosion resistance of Mg-Al matrix increased with decreasing Al content in the matrix. And, it could be regarded that Al content in the matrix is decreased by precipitation of $Mg_{17}Al_{12}$ during the aging treatment and it decreases the anodic reaction rate of the matrix and galvanic effect in AZ91D-T6 alloy. It could be considered that the composition and microstructure of surface protective layer would be varied by precipitation of $Mg_{17}Al_{12}$ and subsequent decreasing of Al content in the matrix. And it would contribute the corrosion resistance of AZ91D-T6 aging alloy.

• Journal of Advanced Research in Ocean Engineering
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• 제2권4호
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• pp.158-168
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• 2016

During the installation of crude oil or gas pipelines, which pass through onshore buried pipelines or onshore pipeline from subsea pipeline to onshore plant, countermeasures need to be implemented so as to ensure a sufficient design life by protecting the steel pipes against corrosion. This can be achieved through impressed current cathodic protection method for onshore pipelines and through galvanic sacrificial anode corrosion protection method for offshore pipelines. In particular, in the case of impressed current cathodic protection, isolation joint flanges should be used. However, this makes maintenance control difficult with its installation having a negative impact on price. Therefore, in this study, the most suitable methodology for onshore pipeline protection between galvanic sacrificial anode corrosion protection and impressed current cathodic protection method will be introduced. In oil and gas transportation facilities, the media can be carried to the end users via onshore buried and/or offshore pipeline. It is imperative for the field operators, pipeline engineers, and designers to be corrosion conscious as the pipelines would undergo material degradations due to corrosion. The mitigation can be achieved with the introduction of an impressed current cathodic protection method for onshore buried pipelines and a galvanic sacrificial anode corrosion protection method for offshore pipelines. In the case of impressed current cathodic protection, isolation joint flanges should be used to discontinuity. However, this makes maintenance control to be difficult when its installation has a negative impact on the price. In this study, the most suitable corrosion protection technique between galvanic sacrificial anode corrosion protection and impressed current cathodic protection is introduced for (economic life of) onshore buried pipeline.

• Corrosion Science and Technology
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• 제18권4호
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• pp.129-137
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• 2019

CFRP (Carbon Fiber Reinforced Plastics) is composed of carbon fiber and plastic resin, and is approximately 20 - 50% lighter than metallic materials. CFRP has a low density, higher specific stiffness, specific strength, and high corrosion resistance. Because of these excellent properties, which meet various regulation conditions needed in the industrial fields, CFRP has been widely used in many industries including aviation and ship building. However, CFRP reveals water absorption in water immersion or high humidity environments, and water absorption occurs in an epoxy not carbon fiber, and can be facilitated by higher temperature. Since these properties can induce volume expansion inside CFRP and change the internal stress state and degrade the chemical bond between the fiber and the matrix, the mechanical properties including bond strength may be lowered. This study focused on the effects of NaCl concentration (0.01 - 1% NaCl) and solution temperature ($30-75^{\circ}C$) on the galvanic corrosion between CFRP and A516Gr.55 carbon steel. When NaCl concentration increases 10 times, corrosion rate of a specimen was not affected, but that of galvanic coupled carbon steel increased by 46.9% average. However, when solution temperature increases $10^{\circ}C$, average corrosion rate increased approximately 22%, regardless of single or galvanic coupled specimen.

• Corrosion Science and Technology
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• 제8권1호
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• pp.40-43
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• 2009

We investigated the corrosion resistance of Zn and Cu coated steel pipes as a substitute for Cu pipe in an air-conditioner system. In addition, the galvanic corrosion tendency between two dissimilar metal parts was studied. The corrosion resistance of the Cu electroplated steel was similar to that of Cu, while the corrosion rate of the Zn electro- galvanized and the galvalume (Zn-55 % Al) coated steels was much higher and not suitable for Cu substitute in artificial sea water and acidic rain environments. Furthermore, the galvanic difference between Cu electroplated steel and Cu was so small that the Cu coated steel pipe can be used as a substitute for Cu pipe in an air-conditioner system.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2741-2744
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• 2003

본 연구에서는 전기 전정 자극(GVS, Galvanic vestibular stimulation)이 일측 전정 기능 소실 환자에게서 정상인과 어떠한 특이성을 보이는가에 대하여 관찰하였다. 실험대상은 14 명(남:5, 여:9)의 일측 전정 기능 소실 환자(경와우절제술 12 례, 전정신경 절제술 2 례)로 자극 방법은 bipolar 로 하여 전류 세기를 1mA에서 3mA 까지 달리하며 실험하였다. GVS 에 대한 반응은 영상 안진기(VOG, Videooculograrh)를 이용하여 관찰하였다. 정상 기능이 있는 측면으로의 자극에 대해서는 정상인과 동일한 반응을 보였으나 일측 전정 기능 소실(unilateral loss)을 갖는 환자의 경우 병변이 있는 쪽에 음의 자극, 없는 쪽에 양의 자극을 가하였을 경우에는 대상자 모두에게서 어떠한 안진 반응도 일어나지 않았다. 자극 후 안진의 경우 정상인은 일반적으로 나타나지 않으나 피검자들에게서는 나타나는 특성을 보였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.3.1-3.1
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• 2011

Nanoengineered materials with advanced architectures are critical building blocks to modulate conventional material properties or amplify interface behavior for enhanced device performance. While several techniques exist for creating one dimensional heterostructures, electrospinning has emerged as a versatile, scalable, and cost-effective method to synthesize ultra-long nanofibers with controlled diameter (a few nanometres to several micrometres) and composition. In addition, different morphologies (e.g., nano-webs, beaded or smooth cylindrical fibers, and nanoribbons) and structures (e.g., core-.shell, hollow, branched, helical and porous structures) can be readily obtained by controlling different processing parameters. Although various nanofibers including polymers, carbon, ceramics and metals have been synthesized using direct electrospinning or through post-spinning processes, limited works were reported on the compound semiconducting nanofibers because of incompatibility of precursors. In this work, we combined electrospinning and galvanic displacement reaction to demonstrate cost-effective high throughput fabrication of ultra-long hollow semiconducting chalcogen and chalcogenide nanofibers. This procedure exploits electrospinning to fabricate ultra-long sacrificial nanofibers with controlled dimensions, morphology, and crystal structures, providing a large material database to tune electrode potentials, thereby imparting control over the composition and shape of the nanostructures that evolved during galvanic displacement reaction.

• International Journal of Concrete Structures and Materials
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• 제8권3호
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• pp.201-212
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• 2014

Sixteen reinforced concrete laboratory specimens were used to evaluate a number of corrosion prevention methods under an accelerated (6 months) testing program. The use of galvanic thermal sprayed zinc, galvanic embedded anodes, a tri-silane sealer, an acrylic coating, and an epoxy/polyurethane coating was evaluated. The specimens received various treatments prior to exposure to accelerated corrosion. The performance of the treatments was evaluated with respect to corrosion currents, chloride ingress, extent of cracking, severity of rust staining, and visual inspection of the reinforcing steel after the conclusion of testing and dissection. Results indicated that the tri-silane sealer, the conjoint use of galvanic thermal sprayed zinc and epoxy/polyurethane coating, the epoxy/polyurethane coating, and acrylic coating performed better than the other methods tested. Higher chloride concentrations were measured in the vicinity of embedded zinc anodes.

• The Korean Journal of Ceramics
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• 제4권3호
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• pp.204-206
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• 1998

The Gibbs free energy of formation of $BaThO_3$ from elemental oxides has been measured at temperatures between 853 and 903 K using a $CaF_2$ solid electrolyte galvanic cell. The galvanic cell consisted of Pt, $O_2, CaO+CaF_2 \parallel CaF_2 \parallelBaThO_3+ThO_2+BaF_2, O_2$, Pt EMF gave the standard Gibbs free energy for the reaction $CaF_2+BaThO_3=CaO+BaF_2+ThO_3$ as $\DeltaG^o$,/TEX>=124111.031-117.597 T(J/mol).

• Journal of Welding and Joining
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• 제17권3호
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• pp.66-70
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• 1999

In order to investigate the quantitative behavior of galvanic corrosion in weld joints between stainless std이 and carbon steel, electrochemical polarization experiments were performed at pH4, pH7 and pH10 with boric acid concentration 4000ppm, and water temperature were selected as $35^{\circ}$C and $60^{\circ}$C. As the results, the galvanic corrosion phenomena of carbon steel weld material at $60^{\circ}$C was revealed $2{1\over2}$ times higher corrosion rate than that at $35^{\circ}$C condition. The corrosion rate of stainless steel was almost inedependent of the variation of pH. The significant corrosion rates of carbon steel and the weld joint of carbon-carbon steel were observed at pH 4.