한국부식방식학회

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전해부식시험을 이용한 니켈-크롬도금강판 및 아연도금강판의 내식성 비교평가시험
An Eectrolytic Corrosion(EC) test method was evaluated by the comparison with Copper Accelerated Acetic Salt Spray(CASS) and Neutral Salt Spray(SS) tests. Those methods were applied in order to evaluate corrosion resistance of Ni-Cr plated and Zn-plated Fe substrates. The correlations between results obtained by different test methods were investigated. Results showed that the electrochemical method such as the EC test method was superior to the conventional methods such as CASS and SS, in terms of the quantitative accuracy and the test-time span. Furthermore, the EC test method provided the useful means to estimate the initiation
of corrosion of each layer by monitoring the rest potentials of the coated layers such as Ni, Cr, and Zn on Fe substrate. With regard to test time spans, the EC test provided the 78 times and 182 times faster results than the CASS test in cases of Fe + 5㎛ Ni + 0.5 ㎛ Cr and Fe + 20 ㎛ Ni + 0.5 ㎛ Cr respectively, while the EC test was 85 times faster results than the Salt Spray test in the case of Fe + 20 g/m2 Zn.
Therefore, the EC test can be the better method to evaluate the resistance to corrosion of coated layers than the conventional methods such as the SS test and the CASS.
KEYWORDs : corrosion resistance, EC test, salt spray, CASS, rest potential
AUTHORs : 이재봉†·김경욱·박민우·송태준·이채승·이의종1·김상열1

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Ta 함량에 따른 Ti-xTa 합금의 부식특성
The purpose of this study was to investigate corrosion characteristics of Ti-xTa alloys with Ta contents. Ti-xTa alloys used as samples (x=30, 40%) were arc-melted under argon atmosphere of 99.9% purity. Ti-xTa alloys were homogenized for 12hr at 1000°C and then water quenched. The surface characteristics of Ti-xTa
alloys were investigated using optical microscopy (OM) and X-ray diffractometer (XRD). The anodic corrosion behaviors of the specimens were examined through potentiodynamic, potentiostatic and galvanostatic test in 0.9 % NaCl solution at 36.5±1°C. After corrosion test, the surface characteristics of Ti-xTa alloys were
investigated using OM. The microstructure of Ti-Ta alloy showed the beta structure with Ta content. The corrosion resistance of Ti alloy was improved by increasing Ta content and the corrosion morphology of Ti-Ta alloy showed that the site attacked by chloride ion decreased from the active to passive region with Ta content. Potential of Ti-40Ta alloy increased as time increased, whereas, current density of Ti-40Ta
alloy decreased as time increased compared to Ti-30 alloy.
KEYWORDs : Ti-Ta alloy, Ta content, potentiodynamic, potentiostatic, galvanostatic, biomaterial
AUTHORs : 김현주·최한철†

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Fe와 galvanic couple된 알루미늄의 내식성에 미치는 마그네슘의 영향
Effects of magnesium and pH on corrosion of aluminum galvanically coupled to iron have studied by using potentio- dynamic and static tests for polarization curves, Mott-Schottky test for analysis of semiconductor property, and GD-AES and XPS for film analysis. Pitting potential was sensitive to magnesium as an alloying element but not to pH, while passive current was sensitive to pH but not to magnesium. It was explained with, instead of point defect model (PDM), surface charge model describing that the ingression of chloride depends on the state of surface charge and passive film at film/solution interface is affected by pH. In addition, galvanic current of aluminum electrically coupled to iron was not affected by magnesium in pH
8.4, 0.2M citrate solution but was increased by magnesium at the solution of pH 9.1. The galvanic current at pH 9.1 increased with time at the initial stage and after the exposure of about 200 minute, decreased and stabilized. The behavior of the galvanic current was related with the concentration of magnesium at the surface. It agreed with the depletion of magnesium at the oxide surface by using glow discharge atomic emission spectroscopy (GD-AES). In addition, pitting potential of pure aluminum was reduced in neutral pH solution where chloride ion maybe are competitively adsorbed on pure aluminum. It was confirmed by the exponential decrease of pitting potential with log of [Cl-] around 0.025 M of [Cl-] and linear decrease of the pitting potential. From the above results, unlike magnesium, alloying elements with higher electron negativity, lowering isoelectric point (ISE), are recommended to be added to improve pitting corrosion resistance of aluminum and its alloys in neutral solutions as well as their galvanic corrosion resistance in weakly
basic solutions.
KEYWORDs : Al-Mg alloys, galvanic corrosion, glow discharge atomic emission spectroscopy, high field model,
AUTHORs : 현영민·김희산†

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NaCl 용액에서 Nb 첨가가 Ti 합금의 부식 거동에 미치는 영향
In this study, the effect of niobium addition on the passivation behavior of Ti alloys in NaCl solution was investigated using various electrochemical methods. An α-phase in Ti alloy was transformed into a β-phase and martensite structure decreased as Nb content increased. The corrosion and passivation current density(+300 mVSCE) decreased as Nb content increased, and thereby a stable passive film was formed
on the Ti alloy. Potential of Ti-xNb alloy in the passive region increased, whereas, current density decreased with time from results of potentiostatic and galvanostatic tests. Also, the corrosion morphology showed the smaller pits as Nb content increased. Consequently, Ti alloy contained high Nb content showed a good resistance to pitting corrosion in 0.9 % NaCl solution.
KEYWORDs : Ti-xNb alloy, passivation, potentiostatic, galvanostatic, corrosion morphology
AUTHORs : 김은실·김원기·최한철†

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합금도금강판 내식성 향상을 위한 UV 경화형 유무기 하이브리드 코팅
According to its merits about high curing speed and low emission of volatile organic compounds, UV curable inorganic-organic coating technology has been developed as an alternative for toxic and carcinogenic chromate- based treatments for years. It is consistently observed that ultra-thin films offer excellent corrosion protection as well as paint adhesion to metals. Based on the tetra-ethylorthosilicate(TEOS) and methacryloxypropyl trimethoxysilane(MPTMS), inorganic sol was synthesized and formed hybrid networks with UV curable acrylic monomer, 6-hexanediol diacrylate(HDDA), trimethylolpropane triacrylate(TMPTA), pentaerylthritol triacrylate(PETA). Several methods were used to test their properties such as salt spray test, potentiodynamic measurement, tape peel test, etc. It was shown that anti-corrosive property and stability of storage were affected by the molecular ratios of inorganic and organic compounds. It was not only the stability of storage, but had a excellent anti-corrosive, paint adhesive, and anti-solvent properties in a final molar ratios of 0.6/0.04/0.86/0.005 (TEOS/MPTMS/Acetone/HNO3) and 0.08/0.106/0.081/0.02 (TMPTA/HDDA/PETA/photo initiator).
KEYWORDs : UV curable, hybrid coating, anti-corrosive, temporary corrosion protection, alloy plating coated
AUTHORs : 박종원†·이경황·나현주·박병규·남영섭·홍신협

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탄소강 볼트 체결된 GECM(Graphite Epoxy Composite Material)/Al 판재 간의 갈바닉 부식 거동
This work focused on galvanic corrosion of carbon steel bolted GECM/Al plates by long-term test in tap water and NaCl solutions. Test product was carbon steel bolted between cross packed GECM and painted aluminium. Tests for the product and coupled parts determined corrosion rate in tap water and NaCl solutions. Also, using
a potentiostat and salt water sprayer, galvanic test was done. In galvanic test on carbon steel bolted GECM/Al plates, corrosion of carbon steel bolt was faster in series of tap water>1% NaCl solution>3.5% NaCl solution. In galvanic couple between aluminium and carbon steel bolt, their corrosion rates were higher than those of single specimen. In galvanic couple between GECM, aluminium, and carbon steel bolt, corrosion behaviors of carbon steel bolt and aluminium were changed due to different corrosion mechanism in tap water and chloride solution.
KEYWORDs : Galvanic corrosion, carbon steel bolted GECM, Al, tap water, NaCl
AUTHORs : 김영식†, 박수진, 유영란

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터보불로워 용 회전체 주축 소재의 마찰, 마모 및 부식 저항 향상을 위한 WC-metal 분말의 초고속화염용사코팅
High velocity oxy-fuel (HVOF) spray coating of WC-metal powder (powder) was carried out to improve the resistances of friction, wear and corrosion of magnetic bearing shaft material Inconel718 (In718) of turbo blower. A micron sized WC-metal powder (86.5% WC, 9.5% Co 4% Cr) was coated onto In718 surface using HVOF thermal spraying. During the spraying, the binder metals and alloy such as Co, Cr
and Co-Cr alloy were molten and a small portion of WC particles were partially decomposed to W2C and free carbon at above its decomposition temperature of 1250ºC. The free carbon and excessively sprayed oxygen formed carbon oxide gases, resulting a porous coating of porosity of 2.2±0.3%. The surface hardness
of substrate increased approximately three times from 400 Hv of In718 to 1260±30 Hv of the coating The friction coefficients of the coating were approximately 0.33 ± 0.03 at 25ºC and 0.26 ± 0.03 at 450ºC. These values were smaller than those of In718 substrate at both temperatures due to the lubrication from the free carbon and the cobalt oxide debris. The corrosion resistance of the coating was higher than that
of In718 both in salt water of 3.5% NaCl and acid of 1 M HCl solutions, on the contrary, it was lower in base solution of 1 M NaOH. According to this study, the HVOF WC-metal powder coating is recommended for the durability improvement of magnetic bearing shaft of turbo blower.
KEYWORDs : Coating, friction, wear, corrosion
AUTHORs : 주윤곤, 윤재홍, 조동율, 천희곤†

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Development of High Functional Black Resin Coated Electrogalvanized Steel Sheet for Digital TV Panel
Recently Digital TV industry has drastically been moving the illuminating system, which causes an obvious product change from PDP and LCD to LED model to provide high-definition image. Due to strong competition in the digital industry, TV manufacturers make a great efforts to reduce production cost by using low-priced
materials such as steels instead of aluminum and plastic etc. In this paper we have developed a new low-priced electrogalvanized steel sheet, which has a black resin
composite layer, to substitute conventional high-priced PCM steel and plastic mold for rear cover panel in the digital TV. The black resin composite was prepared by mechanical dispersion of the mixture solution that consists of high solid polyester resin, melamine hardener, black pigment, micronized silica paste, polyacrylate
texturing particle and miscellaneous additives. The composite solution was coated on the steel sheet using roll coater followed by induction furnace curing and cooling. Although the coated layer has a half thickness compared to the conventional PCM steels having 23㎛ thickness, it exhibits excellent quality for the usage of rear cover panel. The new steel sheet was applied to test products to get quality certification from worldwide electronic appliance customers. Detailed discussion provides in this paper including preparation of composite solution, roll coating technology, induction curing technology and quality evaluation from customers.
KEYWORDs : Digital TV, Composite, PCM steel, Plastic, Black Resin Coated Steel
AUTHORs : Du-Hwan Jo†, Moonjae Kwon, Jae-Hwa Lee, Hee-Seung Kang, Yong-Gyun Jung, Yon-Kyun Song, Min-Hwan Jung, Soo-Hyoun Cho, Yeong-Bong Cho, Myoung-Rae Cho, Byoung-Chon Cho, Kwangsoo Lim, Pan-Woo Seon, Hyeon-Soop Han, Hwon-Woo Jeong, Jae-Ryung Lee, and Jong-Sang Kim

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