한국부식방식학회

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Page : 320 - 325 DOWNLOAD
배관감육 관리를 위한 고정식 및 탈착식 보온재 설치 경제성 분석
To perform ultrasonic testing (UT) thickness measurement of the secondary side piping installed in nuclear power plants, the insulation for preventing heat loss should be removed. The type of insulation can be divided into fixed and removable insulation. Fixed and removable insulation have their own strengths and weaknesses. Removable insulation has been installed in the components susceptible to wall thinning caused by FAC and erosion from Shin-Kori unit 1, which commenced its commercial operation in 2011. In this paper, the number of repeated inspections of components and the number of replacements of fixed insulation were estimated and a more economical way was identified based on the manufacturing and installation costs for fixed and removable insulation.
KEYWORDs : wall thinning, UT inspection, fixed insulation, removable insulation, economic analysis
AUTHORs : 황경모†·윤훈

Page : 314 - 319 DOWNLOAD
Development of Electrochemical Processes for Aluminium-Based Coatings for Fusion Applications
Reduced activation ferritic-martensitic steels (RAFM) are envisaged in future fusion technology as structural material which will be in direct contact with a flowing liquid lead-lithium melt, serving as breeder material. Aluminium-based coatings had proven their ability to protect the structural material from corrosion attack in flowing Pb-15.7Li and to reduce tritium permeation into the coolant, significantly. Coming from scales
produced by hot dipping aluminization (HDA), the development of electrochemical-based processes to produce well-defined aluminium-based coatings on RAFM steels gained increased attention in research during the last years. Two different electrochemical processes are described in this paper: The first one, referred to
as ECA, is based on the electrodeposition of aluminium from volatile, metal-organic electrolytes. The other process called ECX is based on ionic liquids. All three processes exhibit specific characteristics, for example in the field of processability, control of coating thicknesses (low activation criteria) and heat treatment
behavior. The aim of this article is to compare these different coating processes critically, whereby the focus is on the comparison of ECA and ECX processes. New results for ECX will be presented and occurring development needs for the future will be discussed.
KEYWORDs : Al-based coating, corrosion barrier, tritium permeation barrier, ionic liquids
AUTHORs : J. Konys†

Page : 311 - 313 DOWNLOAD
Electrochemical Impedance Study for Selective Dissolution of a Cu-Zn Alloy
The anodic dissolution behavior of copper and brass in an electrolyte solution of 0.5M NaCl containing 0.5 mM NaHCO3 was investigated by electrochemical impedance spectroscopy. The Nyquist plots of the copper impedance described a small loop in the high-frequency range and a large locus in the low-frequency
range. Additionally, the features of the impedance spectrum of the brass were similar to those of the copper. This indicates that the copper-enriched layer formed on the brass surface due to the selective dissolution of the zinc from the surface. In addition, the rest potential and the anodic polarization curve for each sample were measured in order to discuss the selective dissolution of the zinc from the brass surface.
KEYWORDs : Cu-Zn alloy, selective dissolution, dezincification, electrochemical impedance spectroscopy
AUTHORs : Y. Hoshi†, K. Tabei, I. Shitanda, and M. Itagaki

Page : 303 - 310 DOWNLOAD
수돗물 부식성 제어를 통한 수도관 부식방지 : 부식억제제별 효과와 영향에 대한 분석
The tap water used in Seoul was found to be corrosive. Its corrosivity was effectively reduced by that the additions of alkali agent such as NaOH, Ca(OH)2 and corrosion inhibitor such as H3PO4. For the corrosion test, carbon steel pipe 50 m long was exposed to the drinking water produced by a pilot plant at 36.5℃, similar to the existing process where it takes about 20 minutes to reduce the initial chlorine content of 0.5 ㎎/L to 0.05 ㎎/L. CO2 and Ca(OH)2 was added not only to control the Langelier index (LI) above –1.0 and but also, to increase the duration time of residual chlorine by about 6 times. The persistence effect of residual chlorine was in the order of H3PO4 > Ca(OH)2 > NaOH. Measurements of weight loss showed that corrosion inhibition was effective in order of Ca (OH)2 > H3PO4 > NaOH > no addition, where the concentrations of Ca(OH)2 and phosphate were 5 ~ 10 ㎎/L (as Ca2+) and 1 ㎎/L (as PO4 3-), respectively.
KEYWORDs : corrosion, LI, calcium hydroxide, chlorine
AUTHORs : 박영복†·박주현·박은희·이진숙·김현돈·최영준·정현미·허유정·최인철

Page : 297 - 302 DOWNLOAD
졸-겔 법을 통한 수분산형 폴리우레탄 합성 및 가교밀도 개선에 따른 성능 연구
Water-based systems are dominating the coating market because of worldwide VOCs regulations. Research is focusing especially on waterborne polyurethane (WPU) because of its unique mechanical and chemical properties. However, commercial WPU consists of linear thermoplastic polymers with polar groups on the main chain, which do not perform as well as solvent-borne PU in a two-pack
system. In this study, APTES were used as a chain crosslink agent to overcome commercial WPU’s limited performance. WPUs synthesized by using a sol-gel process were evaluated with FT-IR, particle analysis, TGA, tensile tests, pull-off tests, SEM, and EIS. The results showed that WPUs with added APTES had better thermal stability, mechanical properties, and water resistance than did WPUs without
added APTES. Consequently, the sol-gel process increased the crosslink density of WPUs and modified the WPU’s own properties.
KEYWORDs : waterborne polyurethane, sol-gel, crosslink density, EIS, water uptake
AUTHORs : 김영렬·박진환†

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Burn Damage에 따른 도막의 방청성 평가
This study was conducted in order to examine the effect of burn damage and the resultant anti-corrosion performance. The breakdown and defect of the paint film caused by burn damage are considered to affect not only the macroscopic appearance but also the adhesive force and the anti-corrosion performance of
the paint film. The material of the paint film was epoxy paint that is used most widely for heavy-duty coating, and in order to induce burn damage, heat treatment with a torch was applied to the other side of the paint film. Surface and chemical structure changes according to aging were analyzed using FE-SEM and infrared absorption spectroscopy, and variation in the anti-corrosion performance was analyzed through
the AC impedance test.
KEYWORDs : burn damage, temperature, FT-IR, EIS, anti-corrosion evaluation, epoxy paint
AUTHORs : 서창호·박진환†

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Corrosion and Nanomechanical Behaviors of 16.3Cr-0.22N-0.43C-1.73Mo Martensitic Stainless Steel
The effect of nitrogen on the electrochemical corrosion and nanomechanical behaviors of martensitic stainless steel was examined using potentiodynamic polarization and nanoindentation test methods. The results indicate that partial replacement of carbon with nitrogen effectively improved the passivation and pitting corrosion resistance of conventional high-carbon and high- chromium martensitic steels. Post-test observation of the samples after a potentiodynamic test revealed a severe pitting attacks in conventional martensitic steel compared with nitrogen- containing martensitic stainless steel. This was shown to be due to (i) microstructural refinement results in retaining a high-chromium content in the matrix, and (ii) the presence of reversed austenite formed during the tempering process. Since nitrogen addition also resulted in the formation of a Cr2N phase as
a process of secondary hardening, the hardness of the nitrogen- containing steel is slightly higher than the conventional martensitic stainless steel under tempered conditions, even though the carbon content is lowered. The added nitrogen also improved the wear resistance of the steel as the critical load (Lc2) is
less, along with a lower scratch friction coefficient (SFC) when compared to conventional martensitic stainless steel such as AISI 440C.
KEYWORDs : martensitic stainless steel, potentiodynamic polarization, impedance spectroscopy, pitting corrosion, nanomechanical
AUTHORs : Rahul Ghosh†, S. Chenna Krishna, A. Venugopal, P. Ramesh Narayanan, Abhay K. Jha, P. Ramkumar, and P. V. Venkitakrishnan

Page : 271 - 280 DOWNLOAD
An Overview of New Progresses in Understanding Pipeline Corrosion
An approach to achieving the ambitious goal of cost effectively extending the safe operation life of energy pipeline to 100 years is the application of health monitoring and life prediction tools that are able to provide both long-term remnant pipeline life prediction and in-situ pipeline condition monitoring. A critical step is the enhancement of technological capabilities that are required for understanding and quantifying the effects of key factors influencing buried steel pipeline corrosion and environmentally assisted materials degradation, and the development of condition monitoring technologies that are able to provide in-situ monitoring and site-specific warning of pipeline damage. This paper provides an overview of our current research aimed at developing new sensors and electrochemical cells for monitoring, categorising and quantifying the level and nature of external pipeline and coating damages under the combined effects of various inter-related variables and processes such as localised corrosion, coating cracking and disbondment, cathodic shielding, transit loss of cathodic protection.
KEYWORDs : pipeline life prediction, corrosion monitoring, oil & gas pipeline, protective coatings, cathodic
AUTHORs : M. YJ Tan†, F. Varela, Y. Huo, R. Gupta, D. Abreu, F. Mahdavi, B. Hinton, and M. Forsyth

Page : 265 - 270 DOWNLOAD
Ellipso-Microscopic Observation of Titanium Surface under UV-Light Irradiation
The ellipso-microscopic observation of a titanium surface undergoing anodization in 0.05 mol dm-3 of H2SO4 was conducted. During irradiation by ultra-violet (UV) light with a wavelength of 325 nm, the titanium surface allowed for the flow of a photo-induced current and showed up as a bright, patch-like image on an ellipso-microscopic view. The brightness and patch-pattern in the image changed with flowing photo-induced current. The changes in the brightness and the image corresponded to the formation and/or degradation of titanium oxide due to the photo-electrochemical reaction of the oxide. An in situ monitoring using the ellipso-microscope revealed that the film change was dependent on the irradiation light power, by UV-light increases the anodic current and results in the initiation of pitting at lower potentials as compared with the non-irradiated condition.
KEYWORDs : ellipso-microscopy, UV-light, passivity, titanium, photo-corrosion, non-uniformity
AUTHORs : K. Fushimi†, K. Kurauchi, T. Nakanishi, Y. Hasegawa, M. Ueda, and T. Ohtsuka

Page : 259 - 264 DOWNLOAD
Monitoring the Degradation Process of Inconel 600 and its Aluminide Coatings under Molten Sulfate Film with Thermal Cycles by Electrochemical Measurements
With a specially designed electrochemical cell, the changes in impedance behavior for Inconel 600 and aluminide diffusion coatings under molten sulfate film with thermal cycles (from 800 ˚C to 350 ˚C) were monitored with electrochemical impedance measurements. It was found that corrosion resistance for both materials increased with lower temperatures. At the same time, the state of molten salt was also monitored successfully by measuring the changes in impedance at high frequency, which generally represents the resistance of molten salt itself. After two thermal cycles, both Inconel 600 and aluminide diffusion coatings showed excellent corrosion resistance. The results from SEM observation and EDS analysis correlated well with the results obtained by electrochemical impedance measurements. It is concluded that electrochemical impedance is very useful for monitoring the corrosion resistance of materials under molten salt film conditions even with thermal cycles.
KEYWORDs : hot corrosion, molten salt film, thermal cycle, EIS, aluminide diffusion coating, Inconel 600
AUTHORs : S. Take†, S. Yoshinaga, M. Yanagita, and Y. Itoi

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