• 한국표면공학회지
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• 제36권4호
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• pp.301-306
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• 2003

Multilayered WC-Ti/suv $1-x/Al_{x}$ N coatings were deposited on AISI D2 steel using cathodic arc deposition (CAD) method. These coatings contain structural defects such as pores or droplets. Thus, the substrate is not completely isolated from the corrosive environment. The growth defects (pores, pinholes) in the coatings are detrimental to corrosion resistance of the coatings used in severe corrosion environments. The localized corrosion behavior of the coatings was studied in deaerated 3.5 wt.% NaCl solution using electrochemical techniques (potentiodynamic polarization test) and surface analyses (GDOES, SEM, AES, TEM). The porosity was calculated from the result of potentiodynamic polarization test of the uncoated and coated specimens. The calculated porosity is higher in the $WC-Ti_{0.6}$ $Al_{0.4}$ N than others, which is closely related to the packing factor. The positive effects of greater packing factor act on inhibiting the passage of the corrosive electrolyte to the substrate and lowering the localized corrosion kinetics. From the electrochemical tests and surface analyses, the major corrosion mechanisms can be classified into two basic categories: localized corrosion and galvanic corrosion.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.322-323
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• 2012

This study discussed the formation of phosphate conversion coatings on AZ31 Mg alloy (AZ31) from the zinc phosphating bath with various concentrations of sodium fluoride (NaF). The effects of NaF on the formation, structure, composition and electrochemical behavior of the phosphate coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD) weight balances, open circuit potential (OCP) transients, potentiodynamic polarization curves and immersion test. The coatings were composed of two layers: an outer $Zn_2(PO_4)_3.4H_2O$ (hopeite) crystal layer and an inner amorphous of $MgZn_2(PO_4)_2$. NaF concentration is emphasized to be highly effective in the formation of the hopeite crystal and etching and coating rates. Potentiodynamic polarization and immersion test showed that the coatings formed in the zinc phosphating bath with addition of NaF have much higher corrosion resistance than bare AZ31.

• 대한치과보철학회지
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• 제31권3호
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• pp.423-446
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• 1993

Titanium and its alloys are finding increasing use in medical devices and dental implants. The strong selling point of titanium is its resistance to the highly corrosive body fluids in which an implant must survive. This corrosion resistance is due to a tenacious passive oxide or film which exists on the metal's surface and renders it passive. Potentiodynamic polarization measurement is one of the most commonly used electro-chemical methods that have been applied to measure corrosion rates. And the potentiodynamic polarization test supplies detailed information such as open circuit, rupture, and passivation potential. Furthermore, it indicates the passive range and sensitivity to pitting corrosion. This study was designed to compare the corrosion resistance of the commonly used dental implant materials such as CP Ti, Ti-6A1-4V, Co-Cr-Mo alloy, and 316L stainless steel. And the effects of galvanic couples between titanium and the dental alloys were assessed for their useful-ness-as. materials for superstructure. The working electrode is the specimen , the reference electrode is a saturated calomel electrode (SCE), and the counter electrode is made of carbon. In $N_2-saturated$ 0.9% NaCl solutions, the potential scanning was performed starting from -800mV (SCE) and the scan rate was 1 mV/sec. At least three different polarization measurements were carried out for each material on separate specimen. The galvanic corrosion measurements were conducted in the zero-shunt ammeter with an implant supraconstruction surface ratio of 1:1. The contact current density was recorded over a 24-hour period. The results were as follows : 1. In potential-time curve, all specimens became increasingly more noble after immersion in the test solution and reached between -70mV and 50mV (SCE) respectively after 12 hours. 2. The Ti and Ti alloy in the saline solution were most resistant to corrosion. They showed the typical passive behavior which was exhibited over the entire experimental range. Therefore no breakdown potentials were observed. 3. Comparing the rupture potentials, Ti and Ti alloy had the high(:st value (because their break-down potentials were not observed in this study potential range ) followed by Co-Cr-Mo alloy and stainless steel (316L). So , the corrosion resistance of titanium was cecellent, Co-Cr-Mo alloy slightly inferior and stainless steel (316L) much less. 4. The contact current density sinks faster than any other galvanic couple in the case of Ti/gold alloy. 5. Ag-Pd alloy coupled with Ti yielded high current density in the early stage. Furthermore, Ti became anodic. 6. Ti/Ni-Cr alloy showed a relatively high galvanic current and a tendency to increase.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1893-1896
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• 2003

This research aimed to fabricate a micro structure using micro electrochemical machining (${\mu}$-ECM). with a view to that the theory of ${\mu}$-ECM is established accurately in a different way of conventional electrochemical machining. In details, if the impedance is existed in the system, it is difficult to analyze the micro electrochemical reaction efficiently in polarization curve using a potentiodynamic test. Hence, this research investigates the relationships between impedance and electric current measuring with a potentiostatic test applying to a pair or electrode as a constant potential. And this paper examines the influence of temperature of electrolyte on polarization curve for the quantitative analysis of electrochemical reactions.

• 한국자기학회지
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• 제9권4호
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• pp.210-216
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• 1999

본 연구에서는 e-beam evaporator를 사용하여 제조한 CoCrTa/CrNi 박막시편의 자성층 두께에 따른 부식특성과 열처리에 따른 부식특성의 변화를 알아보았다. Potentiodynamic scan을 이용하여 알아본 결과, 자성층 두께가 증가함에 따라 부식전위가 낮아지고, 부동태 전류밀도가 감소함을 알 수 있었다. XRD를 이용한 분석결과에 따르면, 이것은 자성층 두께가 증가함에 따라 (100)면보다 수소과전압이 큰 (0002)면으로 우선 성장했기 때문이다. 열처리에 따른 CoCrTa(400$\AA$) 자성박막의 부식특성 변화를 potentiodynamic scan과 accelerated corrosion chamber test를 이용하여 알아본 결과, 열처리후 박막시편의 내부식성이 우수해짐을 알 수 있었다. 이것은 열처리에 의해 자성층위에 Cr 산화물층이 형성되고, 이 산화물층이 자성층의 보호막으로 작용했기 때문이다.

• Corrosion Science and Technology
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• 제18권6호
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• pp.232-242
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• 2019

In this study, hydrophobically modified fumed silica was added to the PVDF coating to improve corrosion protection performance. Two types of silane modifiers, trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDZ), were used for hydrophobic modification of the fumed silica. The composition of modified fumed silica was analyzed by Fourier transform infrared, X-ray photoelectron spectroscopy, and elemental analysis. The dispersion of modified fumed silica in the PVDF coating was observed by the transmission electron microscopy, and the hydrophobicity of PVDF coating was analyzed by the water contact angle. Surface properties were examined by the field emission scanning electron microscopy and scanning probe microscopy. Potentiodynamic polarization was conducted to confirm corrosion protection performance of PVDF coating in terms of hydrophobically-modified fumed silica contents. As a result, the average surface roughness and the water contact angle of the PVDF coating increased with modifier contents. The results of the potentiodynamic polarization test showed an increase of the E_corr values with increase of the hydrophobicity of PVDF coating. Thus, it clearly indicates that the corrosion protection performance of PVDF coating improved with the addition of the hydrophobic-modified fumed silica that prevents the penetration of moisture into the PVDF coating.

• 대한화학회지
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• 제55권2호
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• pp.268-278
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• 2011

베타 차단제 억제제(atenolol, propranolol, timolol and nadolol)의 존재와 부존 하에서 0.1M HCl 용액에 담긴 알루미늄의 부식작용을 연구하였다. 이 연구에 무게감량, 변전위 편극, 전기화학 임피던스 분석법이 사용되었다. 억제 효과는 억제제의 농도 증가에 따라 증가하였으며, 온도가 증가함에 따라 감소하였다. 모든 억제제들은 Frumkin 등온을 따르는 알루미늄 표면에 흡착되었다. 부식반응은 전하이동과정에 의해 조절됨을 발견하였다. 억제 효과 측정을 위해 사용된 실험방법 들에 대해 조사한 결과 모두 억제효과가 우수하였다.

• Corrosion Science and Technology
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• 제21권2호
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• pp.147-157
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• 2022

Electrochemical characteristics and damage behavior of 6061-T6 aluminum alloy used as a battery housing material for electric vehicles were investigated in solution simulating the acid rain environment with chloride concentrations. Potentiodynamic polarization test was performed to analyze electrochemical characteristics. Damage behavior was analyzed through Tafel analysis, measurement of damage area, weight loss, and surface observation. Results described that corrosion current density was increased rapidly when chloride concentration excceded 600 PPM, and it was increased about 7.7 times in the case of 1000 PPM compared with 0 PPM. Potentiodynamic polarization experiment revealed that corrosion damage area and mass loss of specimen increased with chloride concentrations. When chloride concentration was further increased, the corrosion damage area extended to the entire surface. To determine damage tendency of pitting corrosion according to chloride concentration, the ratio of damage depth to width was calculated. It was found that the damage tendency decreased with chloride concentrations. Thus, 6061-T6 aluminum alloy damage becomes larger in the width direction than in the depth direction when a small amount of chloride is contained in an acid rain environment.

• 한국표면공학회지
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• 제36권1호
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• pp.79-84
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• 2003

$WC-Ti_{1}$ -xA $l_{x}$ N multilayered coatings are performed by their periodically repeated structures of lamellae of WC-Ti/$WC-Ti_{1}$ -xA $l_{x}$ Nmaterials. The $WC-Ti_{1}$ -xA $l_{x}$ N coatings with variable Al content were deposited onto AISI D2 steel by cathodic arc deposition (CAD) method. The electrochemical behavior of multilayered $WC-Ti_{1}$ -xA $l_{x}$ N coatings with different phases (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) was investigated in deaerated 3.5% NaCl solution at room temperature. The corrosion behaviors for the multilayered coatings were investigated by electrochemical techniques (potentiodynamic polarization) and surface analyses (X-ray diffraction (XRD), scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy (GDOES)). In the petentiodynamic polarization test, the corrosion current density of $WC-Ti_{0.5}$$Al_{0.5}$N was lower than others.

• Corrosion Science and Technology
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• 제19권3호
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• pp.115-121
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• 2020

In this study, erosion tests and erosion-corrosion tests of Al5083-H321 aluminum alloy were conducted at various flow rates in seawater. The erosion tests were conducted at a flow rate of 0 to 20 m/s, and erosion-corrosion tests were performed by potentiodynamic polarization method at the same flow rate. Characteristic evaluation after the erosion test was conducted by surface analysis. Characteristic evaluation after the erosion-corrosion test was performed by Tafel extrapolation and surface analysis. The results of the surface analysis after the erosion test showed that surface damage tended to increase as the flow rate increased. In particular, intermetallic particles were separated due to the breakdown of the oxide film at 10 m/s or more. In the erosion-corrosion test, the corrosion current density increased as the flow rate increased. Additionally, the surface analysis showed that surface damage occurred in a vortex shape and the width of the surface damage tended to increase as the flow rate increased. Moreover, damage at 0 m/s, proceeded in a depth direction due to the growth of pitting corrosion, and the damaged area tended to increase due to acceleration of the intermetallic particle loss by the fluid impact.