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Page : 212 - 229
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- Influence of Ethylene Glycol on the Electropolishing of Titanium and the Electrochemical characteristics in PEMFC Environments
- This research investigated the effects of electropolishing on titanium using choline chloride-based deep eutectic sol- vents with varying ethylene glycol molar ratios (1:1, 1:2, 1:3) and applied potentials, as well as the electrochemical characteristics in a PEMFC simulated environment. The analysis of the potentiodynamic polarization curves revealed that a choline chloride to ethylene glycol ratio of 1:3 resulted in the most stable current density and the broadest potential range. This stability was attributed to an increased concentration of active ions participating in the electrochemical reaction, which led to the formation of a significant amount of oxygen-bonded metal-organic com- plexes, thereby stabilizing the dissolution reaction. In titanium (Ti) electropolished under optimal conditions, addi- tional TiO2 crystalline phases were observed. The investigation of the electrochemical characteristics in the PEMFC simulation solution presented that mechanically polished titanium did not meet U.S. Department of Energy stan- dards, whereas the specimens electropolished under optimal conditions did. This improvement is due to the ben- eficial influence of the TiO2 formed during the electropolishing process on the electrochemical characteristics.
- KEYWORDs : Titanium, Eco-friendly electrolyte, Electropolishing, PEMFC, Anti-corrosion
- AUTHORs : Hyun-Kyu Hwang and Seong-Jong Kim†
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Page : 230 - 247
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- Prediction of Electrochemical Characteristics of Metallic Bipolar Plates for PEMFCs Using Machine Learning and Deep Learning Model
- In this research, machine learning and deep learning models were employed to develop a predictive model for the electrochemical characteristics of 316L stainless steel used in metallic bipolar plates of PEM fuel cells (PEMFCs). The results indicated that hydrogen ion concentration (pH) exhibited the strongest correlation with electrochemical characteristics, as determined through SHAP analysis, Spearman correlation analysis, and the random forest model. Furthermore, the interaction between hydrogen ion concentration and hydrofluoric acid significantly decreased corrosion resistance, while hydrogen peroxide enhanced corrosion resistance by forming an oxide film on the surface. When comparing the performance of the MLP, DNN_Adam, and ResNet_Nadam prediction models, the DNN and ResNet models outperformed the MLP model. This superior performance is attributed to the use of appropriate optimizers (Adam and Nadam) and Bayesian optimization techniques to identify the optimal hyperparameters for each model. Notably, the ResNet_Nadam model emerged as the best predictor of electrochemical characteristics, achieving the highest R2 value and showing a difference of less than 10% between training and validation data loss in the learning curve. These findings suggest that a thorough understanding of the independent variable data and the application of optimal parameters can enhance the predictive performance of deep learning models.
- KEYWORDs : Machine learning, Deep learning, Prediction of electrochemical characteristics, Metallic bipolar plate, PEMFCs
- AUTHORs : Dong-Ho Shin and Seong-Jong Kim†
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Page : 248 - 257
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- Investigation of Hydrogen Permeability in Metallic Materials for Bipolar Plates with Noble Coatings for PEMFC/PEMWC Systems
- The growing demand for durable PEM systems (PEMFCs and PEMWEs) has emphasized the significance of corrosion resistance and hydrogen uptake characteristics in metallic bipolar plates. To mitigate degra- dation in corrosive environments, noble metal coatings such as platinum (Pt) and gold (Au) have been applied; however, their effects on hydrogen permeation are not well understood. This study evaluates the hydrogen permeation characteristics of STS470, STS316L, and a titanium alloy using the Devanathan–Sta- churski electrochemical method, both in bare form and with noble metal coatings. Thin layers of Pt and Au were deposited via sputtering, and testing was performed in simulated acidic electrolyte environments rel- evant to PEM operation. The results revealed that STS470 had the highest hydrogen permeability, while the titanium alloy exhibited the lowest. Both Pt and Au coatings significantly reduced hydrogen perme- ation, with Pt demonstrating slightly better performance. Furthermore, these coatings improved corrosion resistance under harsh electrochemical conditions. These findings highlight the dual role of noble metal coatings in reducing hydrogen uptake and enhancing corrosion resistance, providing valuable insights for designing advanced metallic bipolar plates in next-generation PEM systems.
- KEYWORDs : Hydrogen permeation, Bipolar plate, Stainless steel, Titanium alloy, Noble metal coatings
- AUTHORs : Hee-Gun Shin, Jae-Ho Lee, Seung-Pill Jung, Hyun-Yeong Jung, Song Jun Ho, Yeon Joo Hong, Ei Joon Shim, and Hye-Jin Kim†
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Page : 258 - 268
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- 치과용 리튬 디실리케이트 세라믹의 다양한 표면 처리에 따른 표면 특성
- Lithium disilicate ceramics are widely used in dental prosthetics due to their outstanding mechanical prop- erties and aesthetic appeal. Among these materials, the Rosetta® SM blocks manufactured by HASS stand out as a leading choice for CAD/CAM restorations, offering both processability and clinical reliability. This study aims to evaluate the effects of various surface treatment protocols on the surface morphology and characteristics of Rosetta® SM lithium disilicate blocks. Five treatment groups were compared: mechanical polishing, hydrofluoric acid (HF) etching, silane primer application, a combination of HF etch- ing followed by silane application, and a one-step treatment using ammonium polyfluoride (APF) with silane. Surface characteristics were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), nanoindentation, contact angle mea- surement, and X-ray diffraction (XRD). Among the treatment protocols, the combination of HF etching and silane application yielded the most favorable microstructural features for adhesive bonding, charac- terized by well-defined surface roughness and enhanced surface energy. The APF-silane one-step treat- ment also showed promising results, demonstrating reduced technique sensitivity and improved clinical applicability. These findings indicate that the choice of surface treatment significantly influences the adhe- sive interface and may enhance the long-term performance of lithium disilicate ceramic restorations.
- KEYWORDs : Lithium disilicate, Dental ceramic, Surface treatment, Silane,Ceramic morphology
- AUTHORs : 곽해성 · 최한철†
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Page : 269 - 280
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- 기계학습에 기반한 AA1100 합금의 부식에 미치는 환경 영향 분석
- This study explores the effects of three environmental chemical species—Na2S, NaCl, and H2O2 —on the corrosion behavior of AA1100 aluminum alloy using machine learning (ML) techniques. We collected experimental data through a full factorial design that included 27 solution conditions, from which we extracted two key electrochemical parameters: corrosion potential (Ecorr) and corrosion current density (icorr), We trained four regression algorithms—k-nearest neighbor, random forest, support vector regression, and extreme gradient boosting—on this data and compared their performance using root mean squared error. Among these models, the random forest algorithm demonstrated the most accurate predictions for both Ecorr and icorr, leading us to select it for further analysis. To assess the influence of each input variable, we employed SHAP (SHapley Additive exPlanations) analysis. Our findings revealed that NaCl made the greatest positive contribution to Ecorr, while H2O2 significantly increased icorr. In contrast, Na S2 had minimal impact on both corrosion indicators. SHAP interaction plots indicated that Cl⁻ and H2O2 had synergistic effects in accelerating corrosion, while Na2S remained inert. This study highlights the effec- tiveness of interpretable ML approaches in analyzing complex corrosion systems and offers a data-driven perspective for corrosion prediction and material design.
- KEYWORDs : Aluminum alloys, Corrosion, Polarization curve, Machine learning
- AUTHORs : 정용주 · 김민태 · 서정우 · 이주희 · 장희진 · 김희수†
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Page : 281 - 288
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- 치과 임플란트용 타이타늄의 표면처리에 따른 부식특성
- This study evaluated the corrosion characteristics of pure titanium specimens under four surface condi- tions: machined, polished after machining, RBM-treated, and SLA-treated. FE-SEM surface observations showed residual machining debris on the machined surface and parallel scratches on the polished surface, while the RBM-treated surface exhibited irregular depressions of various sizes, and the SLA-treated sur- face revealed a micro-honeycomb structure with nanopores. Surface roughness measurements indicated increasing roughness from 0.27 m on the machined surface and 0.39 m on the polished surface to 1.58 m on the RBM surface and 2.16 m on the SLA surface. According to results of potentiodynamic polarization test, the SLA-treated surface showed the highest corrosion potential (–363 mV) and the low- est corrosion current density (0.87 × 10–9 A/cm2), demonstrating superior corrosion resistance. After the corrosion test, localized pitting-induced collapse was observed on the machined surface, whereas the pol- ished surface appeared relatively intact. No obvious corrosion regions were detected at low magnification on the RBM and SLA surfaces. EDS elemental mapping revealed that Na and Cl were evenly distributed on the machined and polished surfaces, while distinct NaCl crystalline precipitates were observed on the RBM and SLA surfaces.
- KEYWORDs : Dental implant, Titanium, Surface treatment, Surface characteristics, Corrosion
- AUTHORs : 김승표 · 최한철†
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Page : 289 - 298
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- 초고강도 철강소재 내 미량 첨가된 합금원소 (Cr 및 Si)가 제조공정 중 표층 산화물 형성과 3.5% NaCl 수용액 내 부식거동에 미치는 영향
- This study investigated the impact of microalloying with chromium (Cr) and silicon (Si), along with shot blasting, on the formation of surface oxides and the long-term corrosion behavior of ultra-high-strength steel in saline environments. X-ray photoelectron spectroscopy revealed that the combined addition of Cr and Si promotes the development of stable oxides, such as Cr2O3 and SiO2. In contrast, Si-only alloys, despite having a higher Si content, formed less stable oxides like SiOx during the high-temperature anneal- ing process. Electrochemical tests indicated that the Cr-Si-bearing samples exhibited the highest polariza- tion resistance and the lowest corrosion current density, although some fluctuations were noted. This is closely linked to the stable formation of adherent (Fe,Cr)-enriched corrosion products, which can inhibit the penetration of corrosive species. Although the shot-blasting process initially compromised the stability of the surface oxide layer, increasing electrochemical reactivity, corrosion resistance gradually improved over immersion time. In contrast, Si-only samples demonstrated relatively higher electrochemical reactiv- ity due to the formation of unstable Si-containing Fe oxides, characterized by higher defect levels and weaker interfacial adhesion to the steel substrate. These findings offer valuable insights into alloy design strategies for ultra-high-strength steel aimed at enhancing surface stability and long-term corrosion resis- tance in chloride-rich environments.
- KEYWORDs : Ultra-high-strength steel, Cr, Si, Oxidation, Corrosion
- AUTHORs : 백규빈 · 황은혜 · 이세웅 · 김성진†
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Page : 299 - 308
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- 전고체 이차전지용 음극 소재의 개발 동향
- Rechargeable lithium-ion batteries have rapidly evolved, driven by their widespread use in portable elec- tronic devices, electric vehicles, and large-scale energy storage systems. As the demand for higher energy density and improved safety increases, interest in next-generation batteries, particularly all-solid-state bat- teries (ASSBs), has surged. ASSBs replace the flammable liquid electrolytes found in conventional lith- ium-ion batteries with inorganic solid electrolytes, significantly enhancing safety. Additionally, they allow for the use of high-capacity electrode materials, which boosts the overall energy density of the battery sys- tem. Ongoing research focuses on developing suitable solid electrolytes, anodes, and cathodes for ASSB applications. While graphite is commonly used as the anode material in traditional lithium-ion batteries, high-capacity materials such as lithium metal and silicon are being actively explored for ASSBs. Research into anode-free battery systems is also progressing concurrently. This review aims to provide a compre- hensive overview of various anode materials, discussing their characteristics, classifications, current devel- opment status, and exploring future directions for their advancement.
- KEYWORDs : Negative electrode, Anode, Solid electrolyte, All-solid-state battery
- AUTHORs : 김재헌†
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Page : 309 - 318
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- Cerium (III) Oxide – Based Conversion Layer on Galvanized Steel: Preparation and Inhibition Properties Characterization
- This study presents inhibitive protection of commercial cerium (III) oxide (Ce2O3) for a galvanized steel substrate in a corrosive solution. Electrochemical measurements revealed that Ce2O3 at a small content (0.05 wt%) had an inhibitor capacity by forming a protective layer after a short immersion. The morphology and growth of the Ce-rich passive film were subjected to field-emission scanning electronic microscopy (FE-SEM) and x-ray diffraction (XRD) analysis. Results showed round-shaped crystals mainly composed of zincite, simonkolleite, and cerium carbonate. Polarization curves confirmed the inhibitory action of Ce2O3 as a cathodic inhibitor. The cerium (III) oxide was then used as the main composition to prepare a cerium-based conversion layer on a galvanized steel substrate, presenting a homogenous and crystal-shape structure revealed by FE-SEM and EDS analysis. This cerium pretreatment layer can help reinforce the adhesion performance (approved by ASTM D4541 pull-off test standard) and anti-corrosion properties (approved by ASTM B117 salt spray test standard) between the epoxy layer and the galvanized steel substrate.
- KEYWORDs : Galvanized steel, Corrosion, Cerium oxide, Cerium conversion layer, Adhesion
- AUTHORs : Thuy Duong Nguyen, Viet Phuong Nguyen, Ai Nhi Pham Thi, Thuy T.B. Hoang, Anh Truc Trinh, and Thu Thuy Thai†
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Page : 319 - 326
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- Pitting Morphology and Electrochemical Characteristics of 304 Stainless Steel Subjected to High-Temperature Exposure under Salt Spray Conditions
- Stainless steel (STS), which contains over 10.5 wt% chromium (Cr), forms a passive film in various envi- ronments, providing superior corrosion resistance compared to conventional steels. However, exposure to marine atmospheric conditions and prolonged high temperatures can compromise the protective function of this passive film, leading to pitting corrosion. This study investigates the pitting behavior and corrosion characteristics of STS304 specimens using salt spray testing (SST) and electrochemical analysis. SST was conducted on both as-received STS304 specimens and those subjected to high-temperature exposure (H_STS304), with cumulative exposure durations of 200, 300, 400, and 500 hours in 100-hour intervals. Analysis of the 3D surface profiles revealed that the frequency and size of pitting corrosion increased with longer salt spray exposure times, a trend that became more pronounced after high-temperature exposure. Additionally, H_STS304 exhibited a less stable passive region during polarization tests and showed sig- nificant potential fluctuations in open circuit potential (OCP) measurements.
- KEYWORDs : STS 304, Salt Spray Test, Pitting morphology, Corrosion potential, Passive film
- AUTHORs : Ji-Hyeon Kim, Ju-Been Ham, Sae-Deok Seo, SeoWoo Nam, Hee-Chang Seo, and Young-Cheon Kim†
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