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Page : 285 - 291
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- 650 °C 의 SO2 가스 환경 하에서 T22와 T92 강의 고온 부식특성
- In this study, the corrosion characteristics of T22 and T92 steel were investigated in 6O2 + 16CO2 + 2SO2 gas environment at 650 °C. Corrosion characteristics were characterized by weight gain, oxide layer thickness, scanning electron microscope, optical microscope, energy dispersive X-ray spectroscopy, and X-ray diffraction.
T22 and T92 steel tended to stagnate oxide layer growth over time. Oxidation kinetics were analyzed using the data of oxide layer thickness, and a regression model was presented. The regression model was significantly acceptable. The corrosion rate between the two steels through the regression model showed significant difference.
The T92 steel was approximately twice as large as the time exponent and showed very good corrosion resistance compared to the T22 steel. In both steels, the oxide layer mainly formed a Fe-rich oxide layer composed of hematite (Fe2O3), magnetite (Fe3O4), and spinel (FeCr2O4). Sulfide segregation occurred in the oxide layer due to SO2 gas. However, the locations of segregation for the T22 and T92 steel were
different. - KEYWORDs : T22, T92, High-temperature, Corrosion, SO2 gas
- AUTHORs : 정광후·김성종†
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Page : 292 - 299
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- 해수 유속 변화에 따른 Al5052-O와 Al6061-T6 알루미늄 합금의 침식부식 특성
- The hull material of a high-speed ship may cause erosion damage from fluid impact. When physical erosion and electrochemical corrosion combine, erosion corrosion damage occurs. The aluminum ship is vulnerable to erosion corrosion because it can be operated at high speed. Thus, in this study, Al5052-O and Al6061-T6
aluminum alloys for the marine environment were selected as experimental materials. The erosion corrosion resistance of Al5052-O and Al6061-T6 aluminum alloys in seawater was investigated by an erosion test and potentiodynamic polarization test at the various flow rate (0 m/s, 5 m/s, 10 m/s, 15 m/s, 20 m/s). Erosion corrosion characteristics were evaluated by surface analysis, 3D analysis, SEM analysis, and the Tafel extrapolation method. The results of surface damage analysis after the erosion test showed that Al6061-T6 presented better erosion resistance than Al5052-O. The results of the potentiodynamic polarization test at the various flow rate, corrosion current density by Tafel extrapolation presented lower values of Al6061-T6
than Al5052-O. Al5052-O showed more surface damage than Al6061-T6 at all flow rates. Consequently, Al6061-T6 presented better erosion corrosion resistance than Al5052-O. The results of this study are valuable data for selecting hull material for an aluminum alloy vessel. - KEYWORDs : Aluminum alloy, Erosion corrosion, Potentiodynamic polarization experiment, Seawater, Surface damage
- AUTHORs : 김영복·김성종†
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Page : 300 - 311
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- 3.5% NaCl 수용액 내 TWIP강의 부식거동에 미치는 합금원소 (Cu, Al, Si)의 영향
- The corrosion behaviors of twinning-induced plasticity (TWIP) steels with different alloying elements (Cu, Al, Si) in a neutral aqueous environment were investigated in terms of the characteristics of the corrosion products formed on the steel surface. The corrosion behavior was evaluated by measuring potentiodynamic polarization test and electrochemical impedance spectroscopy. For compositional analysis of the corrosion products formed on the steel surface, an electron probe x-ray micro analyzer was also utilized. This study showed that the addition of Cu to the steel contributed to the increase in corrosion resistance to a certain extent by the presence of metallic Cu in discontinuous form at the oxide/steel interface. Compared to the case of steel with Cu, the Al-bearing specimen exhibited much higher polarization resistance and lower corrosion current by the formation of a thin Al-enriched oxide layer. On the other hand, Si addition (3.0 wt%) to the steel led to an increase in grain size, which was twice as large as that of the other specimens,
resulting in a deterioration of the corrosion resistance. This was closely associated with the localized corrosion attacks along the grain boundaries by the formation of a galvanic couple with a large cathode-small anode. - KEYWORDs : Twinning-induced plasticity steel, Corrosion, Polarization resistance, Large cathode-small anode
- AUTHORs : 김시온·황중기†·김성진†
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Page : 312 - 317
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- AA1100의 부식에 미치는 Na2S, NaCl, H2O2 농도의 영향
- The objective of this study was to investigate the corrosion behavior of aluminum (AA1100) in a mixed solution of 0 ~ 0.1 g/L Na2S + 0.3 ~ 3 g/L NaCl + 0 ~ 10 mL/L H2O2. Potentiodynamic polarization tests were performed. Effects of solution compositions on corrosion potential, corrosion rate, and pitting potential of aluminum were statistically analyzed with a regression model. Results suggested that localized
corrosion susceptibility of aluminum was increased in the solution with increasing concentration of NaCl because the pitting potential was lowered linearly with increasing NaCl concentration. On the contrary, H2O2 mitigated the galvanic corrosion of aluminum by increasing the corrosion potential. It also mitigated
localized corrosion by increasing the pitting potential of aluminum. Na2S did not exert a noticeable effect on the corrosion of aluminum. These effects of different chemical species at various concentrations were independent of each other. Synergy or offset effect was not observed. - KEYWORDs : Corrosion, Regression analysis, Hydrogen peroxide, Sodium chloride, Sodium sulfide
- AUTHORs : 이주희·장희진†
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Page : 1 - 7
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- A Study on the Crystalline Boron Analysis in CRUD in Spent Fuel Cladding Using EPMA X-ray Images
- Chalk River Unidentified Deposits (CRUDs) were collected from the Korean pressurized water reactor (PWR) plant (A, B, and C) where the axial offset anomaly (AOA) occurred. AOA, also known as a CRUD-induced power shift, is one of the key issues in maintaining stable PWR plant operations. CRUDs were sampled from spent nuclear fuel rods and analyzed using an electron probe micro-analyzer (EPMA). This paper describes the characteristics of boron-deposits from the CRUDs sampled from twice-burnt assemblies from the Korean PWR. The primary coolant of a PWR contains boron and lithium. It is known that boron deposition occurs in a thick CRUD layer under substantial sub-cooled nucleate boiling (SNB). The results of this study are summarized as follows. Boron was not found at the locations where the existence was confirmed in simulated CRUDs, in other words, the cladding and CRUD boundaries. Nevertheless, we clearly observed the presence of boron and confirmed that boron existed as a lump in crystalline form. In addition, the study confirmed that CRUD existed in a crystal form with a unique size of about 10 μm.
- KEYWORDs : CRUD, PWR, Ultrasonic cleaner, X-ray image mapping, Shielded - EPMA
- AUTHORs : Yang Hong Jung†, Seung-Je Baik, and Young-Gwan Jin
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Page : 8 - 15
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- Corrosion Protection Properties of Cobalt Salt for Water-Based Epoxy Coatings on 2024-T3 Aluminum Alloy
- In this paper, the efficiency and the inhibition mechanisms of cobalt salts (cobalt nitrate and cobalt-exchange silica Co/Si) for the corrosion protection of AA2024 were investigated in a neutral aqueous solution by using the electrochemical impedance spectroscopy (EIS) and polarization curves. The experimental measurements suggest that cobalt cation plays a role as a cathodic inhibitor. The efficiency of cobalt cation was important at the concentration range from 0.001 to 0.01 M. The formation of precipitates of oxides/hydroxides of cobalt on the surface at low inhibitor concentration was confirmed by the Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM/EDS) analysis. EIS measurements were also conducted for the AA2024 surface covered by water-based epoxy coating comprising Co/Si salt. The results obtained from exposure in the electrolyte demonstrated the improvement of the barrier and inhibition properties of the coating exposed in the electrolyte solution for a lengthy time. The SEM/EDS analysis in artificial scribes of the coating after salt spray testing revealed the release of cobalt cations in the coating defect to induce the barrier layer on the exposed AA2024 substrate.
- KEYWORDs : Aluminum alloy, Cobalt-exchange silica, Corrosion inhibition, EIS
- AUTHORs : Thu Thuy Thai†, Anh Truc Trinh†, Gia Vu Pham, Thi Thanh Tam Pham, Hoan Nguyen Xuan
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Page : 16 - 22
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- The Influence of Hydrotalcite Intercalated with Benzoate on UV Stability of Acrylic Coating
- It is important to realize that benzoate was intercalated into hydrotalcite (HTC-Bz) by the co-precipitation method. In this case, acrylic coating with 0.5 wt% HTC-Bz was deposited on carbon steel using the spin coating method. Next, the HTC-Bz structure was characterized by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). In fact, an ultraviolet vision spectroscopy (UV-Vis) was used to determine the benzoate content in HTC-Bz, and the UV absorption ability of HTC-Bz. Using electrochemical techniques, water contact angle measurement, and thermal-gravimetric analysis, we compared the protective properties before and after QUV test, hydrophobicity and the thermal stability of acrylic coating containing HTC-Bz. The obtained results showed that HTC-Bz with a plate-like structure was successfully synthesized; benzoate was intercalated into the interlayer of hydrotalcite with a concentration of 28 wt%. Additionally, it was noted that HTC-Bz has an UV absorption peak at 225 nm. In conclusion, the addition of HTC-Bz enhanced the UV stability, hydrophobicity and the thermal stability of acrylic coating.
- KEYWORDs : Benzoate, Hydrotalcite, Acrylic coatings, UV stability
- AUTHORs : Thuy Duong Nguyen, Anh Son Nguyen, Thu Thuy Thai, Gia Vu Pham, Thi Xuan Hang To†, and Marie-Georges Olivier
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Page : 23 - 30
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- The Paint Prepared Using 2D Materials: An Evaluation of Heat Dissipation and Anticorrosive Performance
- Heat sinks are most widely used in thermal management systems; however, the heat dissipation efficiency is usually limited. Therefore, in order to increase heat dissipation efficiency of the heat sink, the heat-dissipating paint using 2D materials (hexagonal boron nitride (h-BN) and graphene) as thermally conductive additive was designed and evaluated in the present study. The heat dissipation performance of the paint was calculated from temperature difference between the paint-coated and -uncoated specimens mounted on the heat source. The highest heat dissipation performance was obtained when the ratio of h-BN to resin was 1/10 in the paint. In addition, further reduction in the temperature of the test specimen by 6.5 oC was achieved. The highest heat dissipation performance of the paint prepared using graphene was achieved at a 1/50 ratio of graphene to the resin, and a 6.5 oC reduction was attained. In addition, graphene exhibited enhanced corrosion resistance property of heat-dissipating paint by inhibiting the growth of the paint blisters.
- KEYWORDs : Paint, h-BN, Graphene, Thermal dissipation, Corrosion resistance
- AUTHORs : Seok Jin Bhang, Hyunjoong Kim†, An Seob Shin, and Jinhwan Park†
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Page : 31 - 36
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- Electrochemical and Thermal Property Enhancement of Natural Graphite Electrodes via a Phosphorus and Nitrogen Incorporating Surface Treatment
- An efficient wet process approach to modifying natural graphite (NG) electrodes for Li-ion batteries is introduced in this paper. With homogeneous mixing and thermal decomposition of NG with diammonium phosphate ((NH4)2HPO4), phosphorus and nitrogen were successfully incorporated into the surface layer of NG particles. Electron microscopy and X-ray photoelectron spectroscopy analyses demonstrated that the surface was well modified by this process. As a result, the treated NG electrodes exhibited much improved electrochemical performance over pristine NG at two different temperatures: 25 °C and 50 °C. Excellent capacity retention of 95.6% was obtained after 100 cycles at 50 °C. These enhanced properties were confirmed in a morphology analysis on the cross-sections of the NG electrodes after galvanostatic cycling. The improved cycle and thermal stabilities can be attributed to the surface treatment with phosphorus and nitrogen; the treatment formed a stable solid electrolyte interphase layer that performed well when undergoing Li insertion and extraction cycling.
- KEYWORDs : Natural graphite, Surface treatment, Phosphorus and nitrogen incorporation, Solid electrolyte interphase, Lithium battery
- AUTHORs : Kyungbae Kim, Han-Seul Kim, Hyungeun Seo, and Jae-Hun Kim†
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Page : 37 - 42
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- Sensitivity to Intergranular Corrosion According to Heat Treatment of 304L Stainless Steel
- Even though 304 low-carbon (304L) stainless steel was developed to enhance the resistance to intergranular corrosion and stress corrosion cracking, it is occasionally subject to degradation in harsh environments. The degree of sensitization (DOS) of 304L stainless steel was studied as a function of sensitization using a double-loop electrochemical potentiokinetic reactivation (DL-EPR) method. Sensitizing heat treatment was performed in an Ar atmosphere at 500°C, 600°C, and 700°C, with heat treatment times varying from 0 to 96 h. DOS was measured by the ratio of the peak current density value of the forward scan to that of the reverse scan. After the EPR experiment, the specimen surface was observed by scanning electron microscopy and energy dispersive spectroscopy. The DOS of the specimens heat-treated at 600°C increased with heat treatment times up to 48 h and then decreased due to a self healing effect. The DOS was higher in specimens heat-treated at 600°C than those at 500°C or 700°C. Corrosion of the sensitized specimens occurred mainly at the δ-γ phase boundary. The corrosion morphology at the δ-γ phase boundary changed with sensitizing heat-treatment conditions due to differences in chromium activity in γ austenite and δ ferrite.
- KEYWORDs : Intergranular corrosion, Degree of sensitization, Self healing effect, Double loop electrochemical potentiokinetic reactivation, δ-γ phase boundary
- AUTHORs : Hyung-Min Jang, Dong-Jin Kim, and Hong-Pyo Kim†
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