한국부식방식학회

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Page : 317 - 323 DOWNLOAD
CHECWORKS와 ToSPACE 프로그램의 배관감육 해석결과 비교
Assumptions have always been that wall thinning on the secondary side piping in nuclear power plants
is mostly caused by Flow-Accelerated Corrosion (FAC). Recent studies have showed that wall thinning
on the secondary side piping is caused by Liquid Droplet Impingement Erosion (LDIE), Solid Particle
Erosion (SPE), cavitation, and flashing. To manage those aging mechanisms, several software such
as CHECWORKS, COMSY, and BRT-CICERO have been used in nuclear power plants. Korean nuclear
power plants have been using the CHECWORKS program since 1996 to date. However, many site
engineers have experienced a lot of inconveniences and problems in using the CHECWORKS program.
In order to work through the inconveniences and to remedy problems, KEPCO-E&C has developed
a “3D-based pipe wall thinning management program (ToSPACE)” based on the experience of over
30 years in relation to the pipe wall thinning management. This study compares the results of FAC
and LDIE analysis using both the CHECWORKS and ToSPACE programs with respect to validation
of the wall thinning analysis results.
KEYWORDs : Pipe wall thinning, Flow-accelerated Corrosion, Liquid droplet impingement erosion, CHECWORKS, ToSPACE
AUTHORs : 황경모†·윤훈·서혁기

Page : 310 - 316 DOWNLOAD
적층가공 방식으로 제조된 CP-Ti의 캐비테이션 중 부식에 대한 전기화학적 접근
The effect of passive film on corrosion of metals and alloys in a static corrosive environment has been studied by many researchers and is well known, however few studies have been conducted on the electrochemical measurement of metals and alloys during cavitation corrosion conditions, and there are no test standards for electrochemical measurements ‘During cavitation’ conditions. This study used
commercially additive manufactured(AM) pure titanium in tests of anodic polarization, corrosion potential measurements, AC impedance measurements, and repassivation. Tests were performed in 3.5% NaCl solution under three conditions, ‘No cavitation’, ‘After cavitation’, and ‘During cavitation’ condition. When cavitation corrosion occurred, the passive current density was greatly in creased, the corrosion potential largely lowered, and the passive film revealed a small polarization resistance. The current fluctuation by the passivation and repassivation phenomena was measured first, and this behavior was repeatedly generated at a very high speed. The electrochemical corrosion mechanism that occurred
during cavitation corrosion was based on result of the electrochemical properties ‘No cavitation’, ‘After cavitation’, and ‘During cavitation’ conditions.
KEYWORDs : Additive manufactured CP-Ti, Cavitation corrosion, Electrochemical mechanism
AUTHORs : 김기태·장현영·김영식†

Page : 301 - 309 DOWNLOAD
36개월간 국내 옥외폭로시험에 따른 아연도강의 표면외관 변화
If galvanized steel is exposed to an outdoor environment, atmospheric corrosion will occur with time and red rust will form when the sacrificial protection capacity of zinc reaches its limit. With corrosion, the surface appearance of steel changes, and the properties of the exterior materials degrade. In this study, two kinds of galvanized steel, (GA and GI specimens) were subjected to an outdoor exposure test for 36
months in six regions of Korea. Chrominance (color, chroma, and brightness) and glossiness surface analyses were performed. The color change was not significant, regardless of the exposed area or the specimens tested. With increasing exposure times, the GA specimen became blackened by the formation of zinc oxide, and red coloration was increased by the formation of red rust. As the exposure time of GI specimen increased, the surface proceeded to blacken, but no red rust was formed and the color did not change significantly. Regardless of the outdoor exposure area or the specimen, longer exposure times led to lower glossiness, and this behavior appears to be influenced by the formation of zinc oxide.
KEYWORDs : Galvanized steel, Outdoor exposure test, Atmospheric corrosion, Chrominance, Glossiness
AUTHORs : 김기태·김영식†

Page : 292 - 300 DOWNLOAD
3D 유한요소법을 이용한 원전 매설배관 부식결함 탐상기술 개발
The modeling of 3D finite elements based on CAD data has been used to detect sites of corrosion defects in buried pipes. The results generated sophisticated profiles of electrolytic potential and vectors of current distributions on the earth surface. To identify the location of defects in buried pipes, the current distribution on the earth surface was projected to a plane of incidence that was identical to the pipe locations. The locations of minimum electrolytic potential value were found. The results show adequate match between the locations of real and expected defects based on modeling. In addition, the defect size can be calculated by integrating the current density curve. The results show that the defect sizes were 0.74 m2 and 0.69 m2, respectively. This technology may represent a breakthrough in the detection of indirect damage in various cases involving multiple defects in size and shape,
complex/cross pipe systems, multiple anodes and stray current.
KEYWORDs : Nuclear Power Plant, Buried Pipe, Indirect Inspection, FEM, Corrosion
AUTHORs : 김재원·임부택·박흥배·장현영†

Page : 287 - 291 DOWNLOAD
지역난방 시스템의 순환수에 따른 보일러 튜브의 부식 특성
In this study, corrosion behavior of a SA178-A alloy used in the boiler tube of a district heating system
was investigated in different environments where it was exposed to pure water, district heating (DH) water,
and filtered district heating (FDH) water. After the corrosion test, the surface morphology was examined
for observation of the number of pitting sites and pitting area fraction, using a scanning electron microscope.
The DH water and FDH water conditions resulted in a lower corrosion potential and pitting potential, and
revealed a significantly higher corrosion rate than the pure water condition. The pitting sites in the DH
water (pH 9.6) were approximately eighteen times larger than those in the pure water (pH 9.6). Compared
to the DH water, the corrosion potential became more noble in the FDH water condition, where iron ions
were reduced through filtration. However, the corrosion rate increased in the FDH water due to an increased
concentration of chloride ions, which deteriorated the stability of passive film.
KEYWORDs : District heating system, Boiler water, Corrosion, Potentiodynamic polarization
AUTHORs : 홍민기·조정민·송민지·김우철·하태백·이수열†

Page : 279 - 286 DOWNLOAD
8인치 직경의 304L 스테인리스강관의 부식특성에 미치는 제작공정의 영향
Austenitic stainless steels used in nuclear power plants mainly use pipes made of seamless pipes, which depend on imports. The manufacturing process and high cost are some of the problems associated with seamless pipes. Therefore, in this study, the corrosion characteristics of the seamless pipe and the SAW pipe were assessed to determine the safety and reliability of the SAW pipe in a bid to
replace the seamless pipe. Microstructure was analyzed using an optical microscope and the degree of hardness was measured using a Rockwell B scale. Intergranular corrosion resistance was evaluated by ASTM A262 Practice A, C, and E methods. The degree of sensitization was determined using a DL-EPR test. Anodic polarization test was performed in deaerated 1% NaCl solution at 30 oC and
the U-bend method was used to evaluate the SCC resistance in 0.01 M Na2S4O6 at 340 oC and 40% NaOH solution at 290 oC. Weld metal of the SAW pipe specimen showed relatively high degree of sensitization and intergranular corrosion rate. However, annealing to SAW pipes improved the corrosion properties in comparison to that of the seamless pipe.
KEYWORDs : 304L stainless steel, Seamless pipe, Welded pipe, Annealing, Nuclear power plant
AUTHORs : 김기태·허승영·장현영·김영식†

Page : 272 - 278 DOWNLOAD
A Study on the Effect of the ICCP System in Reinforced Concrete Specimens of Slab Type
Reinforced concrete (RC) has been used as a construction material in various environments, such as airports, bridges, and ocean concrete structures, etc. Over time, however, rebar in the concrete is prone to corrosion from environmental forces and structural defects of the concrete. Cathodic protection (CP) was invented
to prevent problems with corrosion and is widely used for different applications. Cathodic protection is divided into two types: sacrificial anode cathodic protection (SACP) and impressed current cathodic protection (ICCP). There are several limitations to the use of sacrificial anode cathodic protection in complex reinforced
concrete structures, including concrete resistivity, throwing power of the CP, and environmental conditions. These limitations can affect the protection performance of SACP. Therefore, we used impressed current cathodic protection in our study. We tested Ti-Mesh, Ti-Rod, and Ti-Ribbon anodes in slab type reinforced concrete specimens. Electrochemical tests were conducted to confirm the impressed current cathodic protection performance under different environmental conditions.
KEYWORDs : Reinforced concrete, Cathodic protection, Concrete resistivity, Throwing power
AUTHORs : Jin-A Jeong, Kwon-Heum Ko†, Mun-Su Kim, and Du-Hyeong Lee

Page : 265 - 271 DOWNLOAD
Analysis of CRUD Flake Applied to Abnormal High Beam Current by Shielded-EPMA
CRUD specimens, scraped from twice-burned fuel cladding in the Korean Nuclear Power Plant, were analyzed using Shielded-EPMA. The principal elements of the CRUD were identified as Ni and Fe, at an approximate ratio of 1.3 Ni/Fe. To investigate the morphology and composition of the pure metallic materials in the CRUD, coolant impurities must be removed. This can be accomplished by
increasing the EPMA current to an abnormally high intensity until the impurities are melted. Normally, EPMA applications are performed at conditions of 20 kV voltage and 20 nA current. But in our study, the applied current was increased up to 1200 nA, over time increments ranging from 5 to 30 seconds. This technique was performed by opening an adjustable aperture for the gun alignment. Results showed
impurities contained in the CRUD material disappeared and pure metal materials, e.g., Ni and Fe, remained. This method presents an innovative way to analyze CRUD.
KEYWORDs : CRUD, Shielded-EPMA, Abnormal beam current, Boling chimney hole, NiFe2O4
AUTHORs : Y. H. Jung†, S. J. Baik, and S. B. Ahn

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The Corrosion Behavior of Anti-Graffiti Polyurethane Powder Coatings
Anti-graffiti coatings have become more important. These layers must guarantee excellent corrosion protection properties, and graffiti must be easily removable, without reducing protection and aesthetic properties. In this study, anti-graffiti and corrosion behavior of two anti-graffiti polyurethane powder coatings were studied.
These layers were deposited on aluminum substrate, with two different surface finishes, smooth, and wrinkled. The action of four different removers are investigated. Graffiti were drawn on coatings by means of red acrylic spray paint. Methyl-ethyl-ketone (MEK) and a “commercial” remover were the most effective solvents, in terms of graffiti removal capability, producing limited change in aesthetical surface aspect for smooth finishing. The wrinkled surface was less resistant. Corrosion protection properties, after removal action and contact with the remover, were evaluate by electrochemical impedance spectroscopy. After approximately 5 hours, coatings were no longer protective due to formation of defects. To simulate the weathering effect, UV-B cyclic test (4 hours of UV exposure followed by 4 hours of saturated humidity at 50 °C) were performed for 2000 hours. Gloss and color changes were measured, and electrochemical impedance spectroscopy measurements were performed after aging and graffiti removal.
KEYWORDs : Organic coatings, Anti-graffiti layer, Powder coatings, Electrochemical impedance spectroscopy
AUTHORs : S. Rossi†, M. Fedel, F. Deflorian, and A. Feriotti

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