한국부식방식학회

Page : 43 - 50 DOWNLOAD
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†

Page : 37 - 42 DOWNLOAD
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†

Page : 31 - 36 DOWNLOAD
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†

Page : 23 - 30 DOWNLOAD
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†

Page : 16 - 22 DOWNLOAD
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

Page : 8 - 15 DOWNLOAD
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

Page : 1 - 7 DOWNLOAD
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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