• Corrosion Science and Technology
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• v.2 no.5
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• pp.233-237
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• 2003

Pickling inhibitors can be used to form an adsorbed layer on the metal surface to hinder the discharge of H^+$ and dissolution of metal ions. Nitrogen-containing inhibitors were selected as corrosion inhibitors for mild steel (MS) in pickling acid process. In this study, the addition of inhibitor, the pickling temperatures and the pickling times were the parameters to investigate the effects on the inhibition efficiency (IE) for MS by using weight loss measurement. Preliminary results show that the IE increased with the increase in pickling time from 10 minutes to 60 minutes, and the IE also increased with the increase in temperature at room temperature and $40^{\circ}C$. At the higher temperature. the IE values are higher and almost independent with the pickling time. Furthermore, the potentiodynamic polarization, open circuit corrosion potential-time and corrosion current-time studies show that nitorgen-containing inhibitor behaves predominantly as cathodic polarization. The roughness test and SEM investigation are also studied in this paper.

• Corrosion Science and Technology
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• v.5 no.2
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• pp.52-61
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• 2006

Recently, much of the current development in surface modification engineering are focused on multilayered coatings. Multilayered coatings have the potential to improve the tribological properties. Four different multilayered coatings were deposited on AISI D2 steel. The prepared samples are designed as $WC-Ti_{0.6}Al_{0.4}N$, $WC-Ti_{0.53}Al_{0.47}N$, $WC-Ti_{0.5}Al_{0.5}N$ and $WC-Ti_{0.43}Al_{0.57}N$. The multilayered coatings were investigated with respect to coating surface and cross-sectional morphology, roughness, adhesion, hardness, porosity and tribological behavior. Especially, wear tests of four multilayered coatings were performed by using a ball-on-disc configuration with a linear sliding speed of 0.017 m/sec, 5.38 N load. The tests were carried out at room temperature in air by employing AISI 52100 steel ball ($H_R=66$) having a diameter of 10 mm. The surface morphology, and topography of the wear scars of samples and balls have been determined by using scanning electron spectroscopy (SEM). Results have showed an improved wear resistance of the $WC-Ti_{1-x}Al_xN$ coatings with increasing of Al concentration. $WC-Ti_{0.43}Al_{0.57}N$ coating with the lower surface roughness and porosity with good adhesion enhanced wear resistance.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.298.2-298.2
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• 2016

가공이 까다로운 소재를 가공하기 위한 공구에 적용하기 위해서 Al의 함량이 높은 AlTiN 소재가 개발되어 적용되고 있으며, 이 소재는 공구의 수명향상을 위한 표면처리 소재로 각광을 받고 있다. 본 연구에서는 음극 아크 증착 시 거대입자가 박막에 증착되어 결함을 만들기 때문에 그 밀도를 낮추기 위해서 음극 아크 증착을 이용하여 공정 변화에 따른 AlTiN 박막의 표면형상을 관찰하고 특성을 평가하였다. 또한 빗각 증착을 적용하여 제작한 AlTiN 박막의 특성을 평가하였다. Al-25 at.%Ti 합금타겟을 음극 아크 소스에 장착하여 AlTiN 박막을 코팅하였다. 시편은 스테인리스 강판(SUS304)과 초경(tungsten carbide; WC)을 사용하였다. 음극 아크 소스에 인가되는 전류가 낮을수록 AlTiN 박막 표면에 거대입자의 밀도가 낮아졌으며, 기판 전압과 공정압력이 높을수록 AlTiN 박막의 표면에 존재하는 거대입자의 밀도가 낮아지는 경향을 보였다. 이를 통하여 거대입자밀도를 낮추는 기초공정을 도출하였다. AlTiN 박막 제작 시 빗각을 적용한 결과 $60^{\circ}$의 빗각을 적용한 다층 박막에서 약 33 GPa의 경도를 보였다. 본 연구를 통해 음극 아크 증착을 이용하여 거대입자의 밀도가 낮은 박막을 제작할 수 있는 공정을 도출하였고, 빗각증착을 적용하면 경도가 향상되는 결과를 확인하였다. 이를 통해 절삭공구 등과 같이 고경도의 코팅물성 유지를 위한 코팅분야에 응용이 가능할 것으로 판단된다.

• Analytical Science and Technology
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• v.10 no.3
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• pp.216-224
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• 1997

In the study of cyclic voltammogram of rubeanic acid, rubeanic acid has two reduction peaks; first peak is similar with that of $S^{2-}$ and thiourea, which is conceded to by HgS, second peak is very weak and unidentified. The study also describes the differential pulse cathodic stripping voltammetric method for the determination of rubeanic acid. The followings were optimal conditions of rubeanic acid for the study : 0.05M borate buffer solution(pH 10.0) ; an accumulation potential of -0.30V(vs. Ag/AgCl); accumulation time of 120sec. : scan rate of 10mV/sec. The detection limit of trace analysis shows $2.7{\times}10^{-8}M$ of rubeanic and at optimal conditions.

• Advances in concrete construction
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• v.2 no.3
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• pp.163-176
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• 2014

Essentially, when electrical current flows easily in concrete that has large pores filled with highly connective pore water, this is an indication of a low resistivity concrete. In concrete, the flow of current between anodic and cathodic sites on a steel reinforcing bar surface is regulated by the concrete electrical resistance. Therefore, deterioration of any existing reinforced concrete structure due to corrosion of reinforcement steel bar is governed, to some extent, by resistivity of concrete. Resistivity of concrete can be improved by using SCMs and thus increases the concrete electrical resistance and the ability of concrete to resist chloride ingress and/or oxygen penetration resulting in prolonging the onset of corrosion. After depassivation it may slow down the corrosion rate of the steel bar. This indicates the need for further study of the effect of electric arc furnace dust (EAFD) addition on the concrete resistivity. In this study, concrete specimens rather than mortars were cast with different additions of EAFD to verify the electrochemical results obtained and to try to understand the role of EAFD addition in influencing the corrosion behaviour of reinforcing steel bar embedded in concrete and its relation to the resistivity of concrete. The results of these investigations indicated that the corrosion resistance of steel bars embedded in concrete containing EAFD was improved, which may link to the high resistivity found in EAFD-concrete. In this paper, potential measurements, corrosion rates, gravimetric corrosion weight results and resistivity measurements will be presented and their relationships will also be discussed in details.

• Journal of the Korean Chemical Society
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• v.46 no.1
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• pp.19-25
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• 2002

We measured the variations of potentials and current densities for several polymers. The results were carefully examined to identify various factors such as temperature and pH to influence the potential and rate. The Tafel slope for anodic dissolution was determined by the polarization effect under these conditions. The optimum conditions were established for each case. The second anodic current density peak and maximum current density were designated as the relative polarization sensitivity $(I_r/I_f)$. The mass-transfer coefficient value $({\alpha})$ was determined by the Tafel slope for anodic dissolution on the basis of the polarization effect under optimum conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.486-486
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• 2009

In this paper, the current-voltage (I-V) curves, such as linear sweep voltammetry (LSV) and cyclic voltammetry (CV), were employed to evaluate the effect of electrolyte concentration on the electrochemical reaction trend. From the I-V curve, the electrochemical states of active, passive, transient and trans-passive could be characterized. And then, we investigated that how this chemical affect the process of voltage-induced material removal in electrochemical mechanical polishing (ECMP) of Copper. The scanning electron microscopy (SEM) and energy dispersive spectroscopy EDS) analyses were used to observe the surface profile. Finally, we monitored the oxidation and reduction process of the Cu surface by the repetition of anodic and cathodic potential from cyclic voltammetry (CV) method in acid- and alkali-based electrolyte. From these analyses, it was important to understand the electrochemical mechanisms of the ECMP technology.

• Journal of Environmental Science International
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• v.15 no.3
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• pp.279-286
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• 2006

Electrokinetic technique was considered in removing arsenic from the abandoned mining tails. In order to estimate the removal characteristics of arsenic, the sequential extraction analysis and desorption experiment were carried out prior to the application of electrokientic process. The result of sequential extraction analysis indicated that the water soluble and exchangeable fraction, easily leachable to ground water, were very low as much as about 2.5% and the fraction except residual (38.3%), possibly extractable under very acidic or alkalic environment, was about 59%. In the result of desorption test using four different kinds of electrolytes, the mixture of citric acid and sodium dodecyl sulfate (SDS) showed the highest desorption efficiency as much as 77.3%. The removal efficiencies of arsenic from mining tailings by electrokinetic process under the different electrolyte environments were slightly low and resulted in the following order: citric acid + SDS (18.6%) > 0.1 $NHNO_3$ (8.1%) > HAc (7.4%) > Distilled water(6.6%). Also, arsenic in soil matrix was moved favorably in the direction of anodic rather than cathodic region, which is opposite trend with cationic metal ions generally existing in soil, because anionic form of arsenic is dominated in acidic soil caused by the movement of acid front form anode.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.313-321
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• 2009

The construction of fiber-reinforced plastic (FRP) boats is decreasing trend since the application of international regulations on the control of marine environmental pollution, which recommended the use of environmentally friendly materials. The aluminum alloy used with material for ship is a superior to FRP. It is environmental friendly, easy to recycle, and provides a high added value to fishing boats. However, the welding for Al alloy materials have many problems, such as deformation by welding heat and effect of the working environment. In this paper, it was carried out welding by robot with welding material of ER5183 and ER5556 on 6061-T6 Al alloy for ship. The mechanical and electrochemical characteristics evaluated for specimen welded by robot. The cathodic polarization trend for the base metal and welding metal showed the effects of concentration polarization due to oxygen reduction and activation polarization due to hydrogen generation. The hardnesses of welding zone and heat affected zone are lower than that of base metal. At the result of tensile test, the specimen welded with ER5183 presented excellent property compared with ER5556.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.194.1-194.1
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• 2016

The present study investigated the effect of zincate treatment time on the dissolution behavior and the deposition of copper by immersion process and electroplating process on AZ31 Mg alloy substrate in a copper pyrophosphate bath. Without zincate pretreatment, the AZ31 Mg substrate quickly dissolved in the copper pyrophosphate solution although an external cathodic current was applied. The copper layers deposited on non-zincate treated AZ31 Mg alloy substrate by both immersion and electroplating processes showed very porous structure and very poor adhesion. With increasing zincate treatment time up to 2 min, the dissolution of AZ31 substrate in pyrophosphate solution rapidly decreased and the deposited copper layer was less porous and exhibited stronger adhesion. The immersion of AZ31 Mg sample in zincate solution for 5 min was found as a critical time for producing a non-porous and adherent electrodeposited copper layer on AZ31 Mg alloy. The optimum zincating time can be determined by observing the open circuit potential (OCP) of AZ31 Mg alloy samples in a copper pyrophosphate electroplating bath. The OCP reached a stable value of about -0.10 V (vs. SCE) after 5 min of immersion in the copper pyrophosphate electroplating solution.