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Page : 43 - 50
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- Effect of KCl(s) and K2SO4(s) on Oxidation Characteristics of the 2.25Cr-1Mo Steel in 10%O2+10%CO2 Gas Environment at 650 °C
- In this study, the effects of KCl(s) and K2SO4(s) on the oxidation characteristics of 2.25Cr-1Mo steel were investigated for 500 h in 10O2 + 10CO2 (vol%) gas environmen at 650 °C. Oxidation kinetics were characterized by weight gain, oxide layer thickness, and fitted models for the experiment data were proposed. The fitted models presented considerable agreement with the experimental data. The oxide layer was analyzed using the scanning electron microscope, optical microscope, and energy dispersive X-ray spectroscopy. The oxidation kinetics of 2.25Cr-1Mo steel with KCl and K2SO4 coatings showed significantly different oxidation kinetics. KCl accelerated the oxidation rate very much and had linear oxidation behavior. In contrast, K2SO4 had no significant effect, which had parabolic kinetics. The oxide layer was commonly composed of Fe2O3, Fe3O4, and FeCr2O4 spinel. KCl strongly accelerated the oxidation rates of 2.25Cr-1Mo steel in the high-temperature oxidation environment. Conversely, K2SO4 had little effect on the oxidation rates.
- KEYWORDs : 2.25Cr-1Mo, KCl, K2SO4, Oxidation, High-temperature
- AUTHORs : Kwang-Hu Jung and Seong-Jong Kim†
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Page : 51 - 56
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- Effect of Ti Intermediate Layer on Properties of HAp Plasma Sprayed Biocompatible Coatings
- The objective of this study was to improve properties of plasma sprayed HAp layer to titanium substrate by introducing an intermediate layer with two different methods. Before applying Zn doped HAp coating on titanium substrate, an intermediate layer was introduced by titanium plasma spray or titanium anodization. Heat treatments were conducted for some samples after titanium intermediate layer was formed. Zn doped HAp top layer was applied by plasma spraying. Three-point bending test and pull-off adhesion test were performed to determine the adhesion of Zn doped HAp coatings to substrates. Long-term credibility of Zn doped HAp plasma sprayed coatings on titanium was assessed by electrochemical impedance measurements
in Hanks’ solution. It was found that both titanium plasma sprayed and titanium anodized intermediate layer had excellent credibility. Strong adhesion to the titanium substrate was confirmed after 12 weeks of immersion for coating samples with titanium plasma sprayed intermediate layer. Samples with titanium anodized intermediate layer showed good bending strength. However, they showed relatively poor resistance against pulling off. The thickness of titanium anodized intermediate layer can be controlled much more precisely than that of plasma sprayed one, which is important for practical application. - KEYWORDs : Hydroxy apatite, Plasma sprayed coating, Intermediate layer, Titanium, Anodization
- AUTHORs : Seisho Take†, Tusyoshi Otabe, Wataru Ohgake, and Taro Atsumi
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Page : 57 - 65
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- Corrosion Resistance of Mg-Added Galvannealed Steel Sheets with Nano-Composite Coating
- As competition among global automakers intensifies, demand for materials that are better in price and performance is increasing. While steel and plastic materials compete for automotive fuel tanks, plastic materials have advantages such as light weight for automobiles. However, they have high prices. Accordingly, in this paper,
four types of Zn-X plated steel sheets, electroplating (X = none, Sn) and alvannealed (X = Fe, Fe-Mg), were manufactured and their applicability as a fuel tank material was evaluated. Nano-composite coating solution with good conductivity was treated on the surface of plated steels using a roll coater and then
cured through induction furnace to improve corrosion resistance. Quality haracteristics such as corrosion resistance, fuel resistance to diverse gasoline and diesel fuels, and seam weldability were evaluated for the above plated steels. Their properties were compared and analyzed with conventional Zn-Ni electroplating
steels. Among the above plated steels, Zn-Fe-Mg galvannealed steels coated with nano-composite coating exhibited better properties than other steels. Detailed experimental results suggest that evenly distributed Mg elements on the coating layer play a key role in the enhanced quality performance. - KEYWORDs : Galvannealed steel, Corrosion resistance, Fuel tank, Automotive steel
- AUTHORs : Du-Hwan Jo†, Sang-Man Yun, Doo-Jin Paik, Myung-Soo Kim, and Moon-Hi Hong†
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Page : 66 - 74
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- Study on Corrosion Law of Large Crude Oil Storage Tank Floor and Risk-Based Inspection and Maintenance Technology
- In this paper, the author\'s team has carried out a comparative experimental study on the corrosion characteristics of Q235 steel commonly used in large-scale storage tanks under the specific bottom water environment found with Russian and Daqing crude oil. It was found that there is a certain degree of uniform or local corrosion on the tank floor depending on the kind of bottom water. The bottom water corrosion of Daqing crude oil is a uniform corrosion caused by carbon dioxide. While the Russian crude oil bottom water corrosion is clearly local corrosion caused by co-corrosion of carbon dioxide and hydrogen sulfide, here the corrosion rate is obviously higher than that caused by Daqing crude oil. There are two modes of storage tank inspection and maintenance that have been currently adopted by Chinese refining and chemical enterprises: a regular inspection mode and a API581-2016 risk-based detection mode. These modes have been effectively combined
to form an intelligent tank inspection and maintenance mode, software tools to support this intelligent inspection and maintenance management have been developed. - KEYWORDs : Large crude oil storage tank, Corrosion, Inspection and maintenance, Information system
- AUTHORs : Fang-Wei Luo†, Ran Ran, and Lei Wang
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Page : 75 - 81
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- Effects of NaCl Concentration and Solution Temperature on the Galvanic Corrosion between CFRP and AA7075T6
- To reduce structural weight, light metals, including aluminum and magnesium alloys, have been widely used in various industries such as aircraft, transportation and automobiles. Recently, composite materials such as Carbon Fiber Reinforced Plastics (CFRP) and Graphite Epoxy Composite Material (GECM) have also been applied. However, aluminum and its alloys suffer corrosion from various factors, which include aggressive ions, pH, solution temperature and galvanic contact by potential difference. Moreover, carbon fiber in CFRP and GECM is a very efficient cathode, and very noble in the galvanic series. Galvanic contact between carbon fiber composites and metals in electrolytes such as rain or seawater, is highly undesirable. Notwithstanding the potentially dangerous effects of chloride and temperature, there is little research on galvanic corrosion according to chloride concentration and temperature. This work focused on the effects of chloride concentration and solution temperature on AA7075T6. The increased galvanic corrosion between CRFP and AA7075T6 was evaluated by electrochemical experiments, and these effects were elucidated.
- KEYWORDs : CFRP, AA7075, Galvanic Corrosion, NaCl Concentration, Solution Temperature
- AUTHORs : S. Y. Hur, K. T. Kim, Y. R. Yoo, and Y. S. Kim†
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Page : 82 - 88
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- Synthesis and Characterization of Hydrotalcite/Graphene Oxide Containing Benzoate for Corrosion Protection of Carbon Steel
- This work examined the corrosion protection performance of benzoate loaded hydrotalcite/graphene oxide (HT/GO-BZ) for carbon steel. HT/GO-BZ was fabricated by the co-precipitation method and characterized by infrared spectroscopy, X-ray diffraction, and scanning electronic microscopy. The corrosion inhibition action of HT/GO-BZ on carbon steel in 0.1 M NaCl solution was evaluated by electrochemical measurements. The benzoate content in HT/GO-BZ was determined by UV-Vis spectroscopy. Subsequently, the effect of HT/GO-BZ on the corrosion resistance of the water-based epoxy coating was investigated by the salt spray test. The obtained results demonstrated the intercalation of benzoate and GO in the hydrotalcite structure. The benzoate content in HT/GO-BZ was about 16%. The polarization curves of the carbon steel electrode revealed anodic corrosion inhibition activity of HT/GO-BZ and the inhibition efficiency was about 95.2%
at a concentration of 3g/L. The GO present in HT/GO-BZ enhanced the inhibition effect of HT-BZ. The presence of HT/GO-BZ improved the corrosion resistance of the waterborne epoxy coating. - KEYWORDs : Corrosion inhibition, Hydrotalcite, Benzoate, Graphene oxide, Waterborne epoxy coatings
- AUTHORs : Thuy Duong Nguyen, Boi An Tran, Ke Oanh Vu, Anh Son Nguyen, Anh Truc Trinh, Gia Vu Pham, Thi Xuan Hang To†, and Thanh Thao Phan
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Page : 89 - 99
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- 스프링클러 구리배관의 공식 파손 억제
- 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
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Page : 100 - 107
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- 조선?해양 기자재용 강재의 내식성에 미치는 분체도장 중 산화물 첨가의 영향
- The demand for powder-coated steel used in the marine industry is increasing owing to their superior corrosion resistance. However, the powder coatings used in commercial products can deteriorate easily by the penetration of brine. In an attempt to suppress brine penetration into the powder coating and significantly increase the
corrosion resistance, three types of oxide particles were added to the coating. Electrochemical impedance spectroscopy tests in 3.5% NaCl solution were performed to evaluate the corrosion behaviors of the powder coating with oxide particles. The results showed that the addition of SiO2 particles to a powder coating
severely decreased the corrosion resistance due to the easy detachment of agglomerated SiO2 particles with a coarse size from the coating layer. In contrast, the TiO2 and SnO2-added coatings showed better corrosion resistance, and the TiO2-added coating performed best in the test conducted at room temperature. However, conflicting results were obtained from tests conducted at a higher temperature, which may be attributed to the effective suppression of brine penetration by the fine SnO2 particles uniformly distributed in the coating. - KEYWORDs : Powder coating, Corrosion, Oxide powder, Electrochemical impedance spectroscopy, Marine industry
- AUTHORs : 박진성 ? 류승민 ? 정영재 ? 김성진†
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Page : 109 - 114
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- 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†
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Page : 115 - 121
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- 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†
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