한국부식방식학회

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하이드라진으로 환원시킨 그래핀을 코팅한 오스테나이트와 마르텐사이트 스테인리스 강 고체고분자형 연료전지 금속 분리판의 전기화학적 특성 평가
Graphene was coated on austenitic and martensitic stainless steels to simulate the metallic bipolar plate of proton exchange membrane fuel cell (PEMFC). Graphene oxide (GO) was synthesized and was reduced to reduced graphene oxide (rGO) via a hydrazine process. rGO was confirmed by FE-SEM, Raman spectroscopy
and XPS. Interfacial contact resistance (ICR) between the bipolar plate and the gas diffusion layer (GDL) was measured to confirm the electrical conductivity. Both ICR and corrosion current density decreased on graphene coated stainless steels. Corrosion resistance was also improved with immersion time in cathodic
environments and satisfied the criteria of the Department of Energy (DOE), USA. The total concentrations of metal ions dissolved from graphene coated stainless steels were reduced. Furthermore hydrophobicity was improved by increasing the contact angle.
KEYWORDs : PEMFC, bipolar plate, graphene, stainless steel, interfacial contact resistance, corrosion resistance
AUTHORs : 차성윤 · 이재봉†

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고온화학세정환경에서 20 % EDTA 용액이 결함 전열관 (Alloy600)에 미치는 영향
The transport and deposition of corrosion products in pressurized water nuclear reactor (PWR) steam generators have led to corrosion (SCC, denting etc.) problems. Lancing, mechanical cleaning and chemical cleaning have been used to reduce these problems. The methods of lancing and mechanical cleaning have limitations
in removing corrosion products due to the structure of steam generator tubes. But high temperature chemical cleaning (HTCC) with EDTA is the most effective method to remove corrosion products regardless of the structure. However, EDTA in chemical cleaning aqueous solution and chemical cleaning environments affects
the integrity of materials used in steam generators. The nuclear power plants have to perform the pre-test (also called as qualification test (QT)) that confirms the effect on the integrity of materials after HTCC. This is one of the series studies that assess the effect, and this study determines the effects of 20 % EDTA aqueous solution on defective tubes in high temperature chemical cleaning environments. The depth and
magnitude of defects in steam generator (SG) tubes were measured by eddy current test (ECT) signals. Surface analysis and magnitude of defects were performed by using SEM/EDS. Corrosion rate was assessed by weight loss of specimens. The ECT signals (potential and depth %) of defective tubes increased marginally. But the lengths of defects, oxides on the surface and weights of specimens did not change. The average corrosion rate of standard corrosion specimens was negligible. But the surfaces on specimens showed traces of etching. The depth of etching showed a range on the nanometer. After comprehensive evaluation of all the results, it is concluded that 20 % EDTA aqueous solution in high temperature chemical cleaning
environments does not have a negative effect on defective tubes.
KEYWORDs : steam generator, high temperature chemical cleaning, EDTA, defective tubes, qualification test, ECT
AUTHORs : 권혁철†

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BIW 전착도장에서의 컴퓨터 시뮬레이션 적용사례
The e-coating to inhibit induced corrosion can deposit a coating not only on the exterior surface but also on the inside of whole metallic components of body-in-white (BIW). But it is difficult to deposit paint films on the inside area because metallic components are multi layered. It may cause shortness of e-coating
thickness. The only way to properly verify e-coating thickness is by performing the use of tear-down prototypes. When paint films’ thickness is inadequate, a structural modification on each metallic component is needed. Verification of the thickness improvement for a structural modification requires much manual effort and leads to increasing development time. Recently, the simulation technology has been developed to predict the e-coating thickness in e-coating field. By applying the simulation to BIW, improvement in paint thickness quality and shortening of development period are expected. The paper explains a validated solution that
allows simulating the effect of design changes to the e-coating thickness and current density, thereby delivering results within a time frame of a few days.
KEYWORDs : e-coating, electrochemical process, e-coating simulation, tear-down prototypes, paint bath characterization
AUTHORs : 손대홍† · 정희진 · 안승호 · 김병수 · 김정연 · 최병삼

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Corrosion Protection Performance of Polyester-Melamine Coating with Natural Wood Fiber Using EIS Analysis
In the present study, polyester-melamine coating systems with natural wood fiber (NWF) were prepared and the effects of NWF on the corrosion protectiveness of the polyester-melamine coating were examined using EIS analysis. From the results, higher average surface roughness was observed with increase of NWF content. Water diffusivity and water uptake into the polyester-melamine coatings with NWF were much higher than that into the pure polyester-melamine coating. The decrease in the impedance modulus |Z| was associated with the localized corrosion on carbon steel, confirming that corrosion protection of the polyester-melamine coatings with NWF well agrees with its water transport behavior.
KEYWORDs : polyester, corrosion protection, EIS, wood fiber, confocal microscopy
AUTHORs : PyongHwa Shin, DuHwan Jo, and MinYoung Shon†

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Relationship between the Applied Torque and CCT to obtain the Same Corrosion Resistance for the Plate and Cylindrical Shape Stainless Steels
Many industries need the universal standard or technique to obtain the identical CCT regardless of specimen geometries. This study aimed to determine an appropriate applied torque to the cylindrical specimen defining the apparatus and the procedure to measure the temperature of initiating crevice corrosion in tubular shape
products such as pipes, tubes and round rods etc; the test method also proved applicable to the plate type specimen. A series of experiments for CCT easurements with the plate type and cylindrical stainless steel specimens of various diameters with different microstructures (austenitic and duplex) and PRENs were conducted
to determine the relationship among geometries on CCT. Thus, the apparatus that could measure the CCT of stainless steels with both plate and cylindrical geometries was newly designed. The use of the apparatus facilitated the same CCT value for both geometries only if the specimens were made of the same alloy.
The applied torque can be calculated for various diameters of the cylindrical specimens using the following relation; Applied torque, Nm = -0.0012D2 + 0.019D + 2.4463 (D; the diameter of cylindrical specimen, mm). However, upwards of 35 mm diameter cylindrical specimens require 1.58Nm, which is the same
torque for the plate type specimen; in addition, this test method cannot be used for cylindrical specimens of less than 15 mm diameter.
KEYWORDs : stainless steel, crevice corrosion temperature (CCT), pitting resistance equivalent number (PREN), applied torque, plate, cylindrical shape
AUTHORs : Hyun Young Chang, Ki Tae Kim, Nam In Kim, and Young Sik Kim†

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Biodegradation of Secondary Phase Particles in Magnesium Alloys:A Critical Review
Magnesium alloys have been extensively studied in recent years for potential biodegradable implant applications. A great deal of work has been done on the evaluation of the corrosion behaviour of magnesium alloys under in vitro and in vivo conditions. However, magnesium alloys, in general, contain secondary phase
particles distributed in the matrix and/or along the grain boundaries. Owing to their difference in chemistry in comparison with magnesium matrix, these particles may exhibit different corrosion behaviour. It is essential to understand the corrosion behaviour of secondary phase particles in magnesium alloys in physiological
conditions for implant applications. This paper critically reviews the biodegradation behaviour of secondary phase particles in magnesium alloys.
KEYWORDs : magnesium alloys, biomaterial, corrosion, secondary phase particles, galvanic corrosion
AUTHORs : M. Bobby Kannan†

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Investigation of the Biodegradable Mechanism of Pure Magnesium Using Electrochemical Impedance Spectroscopy Technique
In this study, electrochemical impedance spectroscopy (EIS) was used to examine the changes in the electrochemical properties of biodegradable pure magnesium implanted into Sprague-Dawley rats for three days. The in vivo test results were compared with those of the in vitro tests carried out in Hank\\\'s, dilute saline and simulated body fluid (SBF) solutions. The in vitro corrosion rates were 20~1700 fold higher, as compared to the in vivo corrosion rates. This discrepancy is caused by biomolecule adsorption on the surface, which prevents the transport of water into the magnesium surface on in vivo testing. Among the in vitro experimental conditions, the corrosion rate in SBF solution had the least difference from the in vivo implanted specimen.
KEYWORDs : biomaterials, magnesium, implantation, corrosion, scanning electron microscopy (SEM)
AUTHORs : Woo-Cheol Kim, Seon-Hong Kim, Jung-Gu Kim†, and Young-Yul Kim

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