• Bulletin of the Korean Chemical Society
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• 제15권2호
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• pp.122-126
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• 1994

Corrosion of brass coated steel cords in the acetonitrile solution of sulfenamide derivatives, N-Cyclohexylbenzothiazole-2-sulfenamide (CBTS), N,N'-Dicyclohexylbenzothiazole-2-sulfenamide (DCBS), N-tert-Butylbenzothiazole-2-sulfenamide (TBBS), N-tert-Amylbenzothiazole-2-sulfenamide (TABS), and N-Oxydiethylbenzothiazole-2-sulfenamide (OBTS) was investigated by potentiostatic anodic and cathodic polarization (Tafel plot), DC polarization resistance, and AC impedance measurements. The corrosion current densities and rates are 1.236 ${\mu}A /cm^2$ and 0.655 MPY for CBTS; 1.881 ${\mu}A/cm^2$ and 0.988 MPY for DCBS; 2.367 ${\mu}A/cm^2$ and 1.257 MPY for TBBS; 3.398 ${\mu}A /cm^2$ and 1.809 MPY for TABS, respectively. OBTS among derivatives under study shows the lowest corrosion density (0.546 ${\mu}A /cm^2$) and the slowest corrosion rate (0.288 MPY). Also, the charge transfer resistances and the double layer capacitances are 275.21 $k{\Omega}{\cdot}cm^2$ and 7.0 ${\mu}F{cdot}cm^{-2}$ for CBTS; 14.24 ${\mu}F{\cdot}cm^2$ and 26 ${\mu}F{\cdot}cm^{-2}$ for DCBS; 54.15 $k{\Omega}{\cdot}cm^2$ and 26 ${\mu}F{\cdot}cm^{-2}$ for TBBS; 0.96$k{\Omega}{\cdot}cm^2$ and 83 ${\mu}F{\cdot}cm^{-2}$ for TABS, respectively. The weaker the electron donating inductive effect of derivatives is and the smaller the effect of steric hindrance is, the more the corrosion of brass coated steel cords in the acetonitrile solution of sulfenamide derivatives is prevented. The above results agree with that observed in the field of tire industry.

• 한국해양공학회지
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• 제27권3호
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• pp.8-14
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• 2013

Although there are various factors that threaten the security of ships, one of the most harmful is corrosion. It is not easy to find corroding areas and the status of corrosion, even though corrosion causes serious problems such as submergence and marine pollution as a result of leaking oil and polluted water. To monitor the corrosion of ships, non-destructive inspection, weight loss coupons, electrical resistance, linear polarization resistance, zero resistance ammeter, and electrochemical impedance spectroscopy have been developed. However, these methods require much time to detect corrosion, and most are not appropriate for real time monitoring. Coating, sacrificial anode, and impressed current cathodic protection (ICCP) methods have been developed to control corrosion. The ICCP and sacrificial anode methods are the most popular ways to prevent ship corrosion. However, ICCP is only appropriate for the outside of a ship and cannot be used for complex structures such as ballast tanks because these are composed of many separate chambers. Sacrificial anodes have to be replaced periodically. This paper proposes an integrated corrosion monitoring and control system (ICMCS) that can detect corrosion in real time and is appropriate for complex structures such as ballast tanks. Because the system uses titanium for an anode, exhausted anodes do not need to be replaced.

• 한국표면공학회지
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• 제46권6호
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• pp.271-276
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• 2013

The demand for stainless steel is continuously increasing with the development in offshore industry due to its excellent corrosion resistance characteristics. However, it suffers cavitation-erosion in application of high rotating fluid and the damage accelerates in combination with electrochemical corrosion because of Cl-ion in sea water. This paper investigated the complex damage behavior for 431 stainless steel, that is one of martensite stainless steels, through the hybrid test in sea water. Various experiments were carried out, including potential measurement, anodic/cathodic polarization experiment and Tafel analysis. Surface morphology was observed and damage depth was analyzed by SEM and 3D microscope after each experiment, respectively. The results revealed that more active potential was observed under cavitation condition than static condition due to breakdown of passive film and activation of charge transfer, and that higher corrosion current density was obtained under cavitation condition due to synergistic effect of corrosion and erosion.

• Corrosion Science and Technology
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• 제5권2호
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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.

• Advances in concrete construction
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• 제2권3호
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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.

• 한국세라믹학회지
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• 제44권12호
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• pp.703-709
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• 2007

We evaluate and compare the power generating characteristics of the anode supported SOFCs which have been fabricated from KIST and FZ-Julich in Germany. The performance and electrochemical property of each unit cell was characterized at the temperature range of $650-850^{\circ}C$ under same operating conditions and its microstructural property was thoroughly investigated via SEM after the performance test. According to the investigation, KIST- and FZJ SOFC showed different power generating characteristics in their temperature dependances due to their different design of electrode microstructure, especially the cathode microstructure. FZJ SOFC showed better performance at high temperature while showed lower performance at lower temperature. From the investigation about the correlation between microstructure and electrochemical property, we found that the superior performance of FZJ SOFC at high temperature was mainly due to its lower cathodic polarization resistance whereas better performance of KIST SOFC at lower temperature was mostly attributed to the lower ohmic resistance.

• 한국세라믹학회지
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• 제38권1호
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• pp.45-51
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• 2001

고체산화물 연료전지의 삼상 계면의 길이를 증가시키기 위해 Glycine-Nitrate Process(GNP)를 이용하여 환원극 재료인 L $a_{0.5}$S $r_{0.5}$Mn $O_3$(LSM)과 전해질 재료인 C $e_{0.8}$G $d_{0.2}$ $O_{1.9}$(CGO)를 합성하였다. 적당한 합성조건을 찾기 위하여 글리신의 양을 달리하여 분말을 합성한 결과 LSM의 경우 글리신이 양이온 몰수의 2배일 때 perovskite상이 얻어졌으며 비표면적은 34$m^2$/g 이었다. 합성된 LSM과 CGO 분말을 50:50 wt%로 혼합하여 제작된 환원극을 screen-printing법으로 코팅한 후 각각 1200, 1300, 1350 및 140$0^{\circ}C$에서 4시간 동안 소결한 후 80$0^{\circ}C$에서 power density와 양극과전압 등을 측정한 결과 130$0^{\circ}C$에서 소결한 단위전지에서 최대 309 mW/$ extrm{cm}^2$의 power density를 얻을 수 있었다.다.

• 분석과학
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• 제8권4호
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• pp.723-730
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• 1995

Cyclic voltammetry and in situ STM were employed to examine the interfacial structures of a Pt(111) electrode in 0.1 mM KCN (pH9.5) and 0.1 mM KSCN (pH7) solutions. In situ STM atomic resolution revealed well ordered (2${\surd}$3${\times}$2${\surd}$3)$R30^{\circ}$-6CN and ($2{\times}2$)-2SCN structures within the double layer charging region. Six CN adsorbates formed a hollow hexagon, which embraced a coadsorbed $K^+$ cation. In contrast, the coadsorbed $K^+$ cations on the SCN covered Pt(111) were poorly ordered, despite adsorbed SCN formed a long range ordered ($2{\times}2$)-2SCN adlattice. In situ STM revealed the pronounced influence of potential in controlling the structures of compact layers at the proximity of a Pt electrode. Cathodic polarization facilitated the replacement of the coadsorbed cations by protons.

• 한국표면공학회지
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• 제45권6호
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• pp.272-277
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• 2012

The hull of a fast sailing aluminium ship are generally prone to erosion owing to the impact of seawater. At this time, synergistic effects of the erosion and the corrosion by aggressive ions such as chlorides tend to aggravate the damage. There have been various attempts, including selection of erosion-resistant materials, cathodic protection and addition of corrosion inhibitors, to overcome damage by erosion or corrosion under marine environments. These approaches, however, have limits on identifying the damage mechanism clearly, because they depend on analogical interpretation by correlating two damage behaviors after the individual studies are assessed. In this research, it was devised a hybrid testing apparatus that integrates electrochemical corrosion test and cavitation test, and thus the erosion-corrosion behavior by cavitation was investigated more reliably. As a result, the slightest damage was observed at the potentials between -1.6 V and -1.5 V. This is considered to be due to a reflection or counterbalancing effect caused by collision of the cavitation cavities and the hydrogen gas formed by activation polarization.

• 한국수산과학회지
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• 제16권3호
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• pp.239-245
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• 1983

Electrochemical adsorption always was accompanied with solvent displacement and relative size factor(x) of adsorbate and solvent and hydrogen coverage(${\theta}$) on the lead anodic film electrode formed in phosphoric acid in NaCl solution and the sea water at $15{\sim}35^{\circ}C$ were studied by means of constant current-potential method and potentiodynamic cathodic polarization method. In this experiment, various constants and thermodynamic quantities calculated from the hydrogen coverage were also described to explain the reactivities of di-iso-butylnitrosoamine(DBNA) and proton ($H^+$) according to the changes of interactions between solute and solvent in the bulk phase and interphase. It was investigated that the average values of relative size factor and the coverage of hydrogen atoms studied with the electrode of lead anodic film formed in phosphoric acid solution in 60mM DBNA+0.5M NaCl and in 60mM DBNA+$6\%0$ sea water were about 11.0 and 0.2 respectively. Hydrogen evolution was electrochemical mechanism because of substitutional adsorption of aromatic substance with their delocalization of electrons, but in the case of non-charge transfer adsorption of aliphatic substance(DBNA) interacting relatively little with the electrode, it was combination mechanism.