한국부식방식학회

HOME > >

Page : 163 - 163 DOWNLOAD
Erratum to: 스프링클러 구리배관의 공식 파손 억제
Erratum to: CORROSION SCIENCE AND TECHNOLOGY, Vol. 19, No. 2(2020), pp. 89~99
DOI: https://doi.org/10.14773/cst.2020.19.2.89

The inhibition of pitting corrosion failure of copper sprinkler tubes in wet sprinkler systems was studied. First, an apparatus and technology for removing air in the sprinkler tubes by vacuum pumping and then filling the tubes with water were developed. Using this apparatus and technology, three methods for inhibiting
the pitting corrosion of the copper sprinkler tubes installed in several apartment complexes were tested. The first one was filling the sprinkler tubes with water bubbled by high-pressure nitrogen gas to reduce the dissolved oxygen concentration to lower than 2 ppm. In the second method, the dissolved oxygen concentration of water was further reduced to lower than 0.01 ppm by sodium sulfite. In the third method, the sprinkler tubes were filled with benzotriazole (BTAH) dissolved in water. The third method was the most effective, reducing the failure frequency of the sprinkler tubes due to pitting corrosion by more than 80%. X-ray
photoelectron spectroscopy analyses confirmed that a Cu-BTA layer was well coated on the inside surface of the corrosion pit, protecting it from corrosion. A potentiodynamic polarization test showed that BTAH should be very effective in reducing the corrosion rate of copper in the acidic environment of the corrosion
pit.
KEYWORDs : Copper sprinkler tube, Pitting corrosion inhibition, Nitrogen bubbling, Sodium sulfite, Benzotriazole
AUTHORs : 서상희†, 서영준, 이종혁, 권혁상

Page : 156 - 162 DOWNLOAD
타이타늄 합금에서 산소발생전위 지연이 부동태 피막 특성과 국부부식 저항성에 미치는 영향
The objective of this study was to investigate delayed oxygen evolution and localized corrosion resistance of titanium alloys by performing potentiodynamic polarization, potentiostatic polarization, and Mott-Schottky measurements. Delayed oxygen evolution was compared among titanium alloys, 316 stainless steel, and platinum. Difference in delayed oxygen evolution between titanium alloys and other metals was attributed to specific surface characteristic of each metal. Delayed oxygen evolution of titanium alloys resulted from the predominant process of ionic conduction over electronic conduction. The effect of oxygen evolution on localized corrosion of titanium alloys was investigated using electrochemical critical localized corrosion temperature (E-CLCT) technique. Mott-Schottky measurement was performed to clarify the difference in film properties between titanium alloys and stainless steels. Titanium alloys were found to have much lower donor density than
stainless steels by 1/28. These results indicate that delayed oxygen evolution has little influence on the concreteness of passive film and the resistance to localized corrosion of titanium alloys.
KEYWORDs : Corrosion, Oxygen evolution, Titanium, Polarization, Mott-Schottky
AUTHORs : 오유수 ･ 서동일 ･ 이재봉†

Page : 146 - 155 DOWNLOAD
F316 오스테나이트 스테인리스강의 상변태 및 입계부식저항성에 미치는 입열의 영향
To elucidate the effect of heat inputs on phase transformation and resistance to intergranular corrosion of F316 austenitic stainless steel (ASS), thermodynamic calculations of each phase and time-temperature-transformation diagram were conducted using JMaPro simulation software, oxalic acid etch test, double-loop electrochemical potentiokinetic reactivation test (DL-EPR), field emission scanning electron microscopy with energy dispersive spectroscopy, and transmission electron microscopy analyses of Cr carbide (Cr23C6), austenite phase and ferrite phase. F316 ASS containing a relatively low C content of 0.043 wt% showed a slightly sensitized microstructure (acceptably dual structure) due to a small amount of Cr carbide precipitated at heat affected zone irrespective of heat inputs. Based on results of DL-EPR test, although heat input was increased, the ratio of Ir to Ia was only increased very slightly due to a slight sensitization. Therefore, heat inputs have
little influences on resistance to intergranular corrosion of F316 austenitic stainless steel containing 0.043 wt% C.
KEYWORDs : Stainless steel, DL-EPR, Heat input, δ-ferrite, Cr-carbide
AUTHORs : 정규석† ･ 이인성 ･ 김순태

Page : 138 - 145 DOWNLOAD
Alloy 600의 결정립계 산화에 대한 표면 변형의 영향
Immersion tests of Alloy 600 were conducted in simulated primary water environments of a pressurized water reactor at 325 °C for 10, 100, and 1000 h to obtain insight into effects of surface deformation on internal and intergranular (IG) oxidation behavior through precise characterization using various microscopic
equipment. Oxidized samples after immersion tests were covered with polyhedral and filamentous oxides. It was found that oxides were abundant in mechanically ground (MG) samples the most. The number density of surface oxides increased with time irrespective of the method of surface finish. IG oxidation occurred in mechanically polished (MP) and chemically polished (CP) samples with thin internal oxidation layers. However, IG oxidation was suppressed with relatively thick internal oxidation layers in MG samples compared to MP and CP samples, suggesting that MG treatment could increase resistance to primary water stress corrosion cracking (PWSCC) from the standpoint of IG oxidation. As a result, appropriate surface treatment for Alloy 600 could prevent oxygen diffusion into grain boundaries, inhibit IG oxidation, and finally induce its high PWSCC resistance.
KEYWORDs : Alloy 600, PWSCC, Surface deformation, Immersion test, Intergranular oxidation
AUTHORs : 하동욱 ･ 임연수† ･ 김동진

Page : 131 - 137 DOWNLOAD
ToSPACE 프로그램을 이용한 FAC 해석결과와 실험결과 비교
A number of piping components in the secondary system of nuclear power plants (NPPs) are exposed to aging mechanisms, such as flow-accelerated corrosion (FAC), cavitation, flashing, solid particle erosion, and liquid droplet impingement erosion. Those mechanisms may lead to thinning, leaking, or rupture of the components. Due to the pipe ruptures caused by wall thinning in Surry unit 2 in the USA in 1986 and Mihama unit 3 in Japan in 1994, pipe wall thinning management has emerged as one of the most important issues in the nuclear industry. To manage pipe wall thinning, a foreign program has been utilized for NPPs in Korea since 1996. As our experience and knowledge of pipe wall thinning management have accumulated, our program needs to reflect our experience, requests from users, and the result of recent experiments using Flow Accelerated Corrosion Testing System (FACTS). FACTS is the empirical experimental facility developed by Korea Atomic Energy Research Institute (KAERI) for tests. Accordingly, KEPCO-E&C developed a 3D-based pipe wall thinning management program called ToSPACE in 2016. This paper describes a comparison between the FAC analysis results using ToSPACE and the experimental results using FACTS to verify their applicability to pipe wall thinning management in NPPs.
KEYWORDs : ToSPACE, FACTS, Pipe Wall Thinning, Flow-Accelerated Corrosion (FAC), FAC Experiment
AUTHORs : 황경모† ･ 윤훈 ･ 서혁기 ･ 정의제 ･ 김경모 ･ 김동진

Page : 122 - 130 DOWNLOAD
지역난방 열수송관 국부 부식 파손 분석
In this study, a corrosion failure analysis of a heat transport pipe was conducted, as the result of a pinhole leak. Interestingly, the corrosion damage occurred externally in the pipeline, resulting in severe thickness reduction near the seam line. Also, while a stable magnetite protective film formed on the inner surface, the manganese oxide formation occurred only on the outer surface. The interior and exterior of the pipe were composed of ferrite and pearlite. The large manganese sulfide and alumina inclusions were found near the seam line. In addition, the manganese sulfide inclusions resulted in grooving corrosion, which progressed in the seam line leading to the reduction in the thickness, followed by the exposure of the alumina in
the matrix to the outer surface. To note, the corrosion was accelerated by pits generated from the boundaries separating the inclusions from the matrix, which resulted in pinhole leaks and water loss.
KEYWORDs : District heating, Heat transport pipe, Localized corrosion, Inclusion
AUTHORs : 김유섭 ･ 채호병 ･ 김우철 ･ 정준철 ･ 김희산 ･ 김정구 ･ 이수열†

Page : 115 - 121 DOWNLOAD
해수 환경에서 Al5083-H321 알루미늄 합금의 침식부식 손상에 미치는 유속의 영향과 손상 메카니즘
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.
KEYWORDs : Aluminum alloy, Erosion corrosion, Flow rate, Potentiodynamic polarzation test, Seawater
AUTHORs : 김영복 ･ 김성종†

Page : 109 - 114 DOWNLOAD
3 wt% NaCl 수용액에서 알루미늄과 스테인리스강의 부식에 따른 광 반사 거동
The photo-reflectance of aluminum and AISI 304 stainless steel during cyclic immersion test in 3 wt% NaCl solution was examined in this study. Overall, corrosion was not recognized by a visual inspection or weight measurement up to 310 h. When evaluated, it was noted that the roughness of the specimens did not change significantly. However, localized corrosion, which is located at the vicinity of intermetallic precipitation of aluminum or at the grain boundary of stainless steel, was confirmed by the use of an optical microscope and scanning electron microscopy after tens of hours of utilizing the corrosion test. In this respect, an increase of the peak intensity for metallic Al after 90 h of test, and for metallic Fe after 153 h was detected from the X-ray photoelectron spectra. In this context, it was shown that from the photo-reflectance spectra, the reflection of the visible light from the tested samples was changed noticeably over the test duration. As a result, the intensity of reflected light was decreased up to 90 h ~ 153 h, and thereafter was shown to increase higher than the initial intensity before the corrosion test.
KEYWORDs : Aluminum, Stainless steel, Photo-reflection, Localized corrosion, Salt solution
AUTHORs : 조수연 ･ 나현규 ･ 조혜리 ･ 문종주 ･ 안태정 ･ 장희진†

<
1
>