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Page : 315 - 323
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- 지역난방 구리난방환수관의 공식 원인 분석
- This work examined pitting corrosion failure of a copper heat-return pipe used in a district heating system. The copper pipe was corroded with a 48% reduction in thickness due to localized corrosion on the inner surface exposed to heating water of 20 ~ 40 oC. Fe and Si elements as corrosion products were found around pits. Cl element was also observed, which accelerated oxidation of copper inside pits. Cu 2 O depos-its on the pit’s bottom surface decreased the pH inside the pit. X-ray diffraction analysis revealed hematite, cuprite, malachite and brochantite as corrosion products. Chemical analysis demonstrated that Fe and Si elements did not exist in the copper, supply water, or heating water, indicating that Fe and Si species might have entered into the pipe from the exterior. These results indicated that pits were initiated due to ion concentration gradient near Fe and Si species. Moreover, the interior of pits had lower pH due to Cl - con- centration and Cu2O reactions, which accelerated the pit’s growth and led to formation of pinholes. Additionally, we confirmed that the type of pitting corrosion was a complex combination of types I and II based on the HCO3-/SO42-ratio, pH, temperature, and corrosion products.
- KEYWORDs : Copper, Pitting corrosion, Failure, Heat-return pipe, District heating
- AUTHORs : 이근형·송민지·강태욱·김우철·김희산·이수열†
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Page : 334 - 342
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- 고체전해질과 양극의 계면 열화 반응
- The need for efficient and sustainable energy storage solutions has emerged due to a rapidly increasing energy demand and growing concerns about environmental issues. Among various energy storage methods, lithium secondary batteries are widely used in a variety of electronic devices such as smartphones, laptops, electric vehicles, and large-scale power storage systems due to their high energy density, long lifespan, and cost competitiveness. Recently, all-solid-state batteries (ASSBs) have attracted great attention because they can reduce the risk of fire associated with liquid electrolytes. Additionally, using highcapacity alternative anodes and cathodes in ASSBs can enhance energy density. However, ASSBs that use solid electrolytes experience a degradation in their electrochemical performances due to resistance at solidsolid interfaces. These interfaces can also result in poor physical contact and the presence of products formed from chemical and electrochemical reactions. Solving this interface problem is a critical issue for the commercialization of ASSBs. This review summarizes interfacial reactions between the cathode and solid electrolyte, along with research aimed at improving these interactions. Future development directions in this field are also discussed.
- KEYWORDs : Interfacial reaction, Cathode, Solid electrolyte, All-solid-state battery
- AUTHORs : 김재헌†
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Page : 343 - 351
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- Corrosion Protection Effectiveness and Adsorption Performance of Whey Inhibitor with Cocoa for Mild Steel in Hydrochloric Acid Environment
- A weight loss technique was used to stabilize whey protein (97%) with a small percentage of cocoa (3%) and bond it to a mild steel surface in hydrochloric acid at temperatures ranging from 303 K to 333 K. Results of analyzing whey inhibitor’s effectiveness showed the highest percentage (90%) at a temperature ranging from 30 oC to 60 oC and an amount of 15 grams, leading to outstanding corrosion resistance prop- erties. The efficiency of the inhibitor increased with increasing concentration but decreased with increas- ing temperature. To evaluate corrosion areas, samples were subjected to cross-section analysis before and after adding the inhibitor. The contact angle test conducted on steel alloys indicated that the angle decreases with increasing inhibitor concentration. Adhesion of the samples was also examined after add- ing the inhibitor. Results showed that the best area removal was 11.692%. hen examining the inhibitor using FTIR spectroscopy, the whey protein with cocoa showed a great efficiency. Thus, whey inhibitor can be used as a corrosion inhibitor for mild steel alloys immersed in acidic conditions.
- KEYWORDs : Corrosion inhibition, Whey Protein, Weight loss, Mild steel
- AUTHORs : Hawraa W. Abd Muslim, A. M. Mustafa, and F. F. Sayyid†
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Page : 352 - 364
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- Evaluation of Corrosion Effects in Diesel-Biodiesel and Diesel-Biodiesel-HVO Blends on Metals for Fuel Storage Systems
- Indonesia has implemented B35, as a mixture of 35% biodiesel and 65% diesel fuel. Considering the potential of higher biodiesel blends, it is important to explore the use of hydrotreated vegetable oil (HVO) in fuel blends. HVO can improve cetane number, heating value, sulfur content, and oxidation stability. However, further research is needed, particularly regarding compatibility of materials used in storage and distribution systems. Common materials include stainless steel, carbon steel, and brass. This study aimed to assess effects different fuel mixtures on corrosion rates of stainless steel 304, carbon steel SA 516 Gr.70, and brass immersed in B30, B30D10 (30% biodiesel, 60% diesel fuel, and 10% HVO), and B40. Corro- sion rates were tested using ASTM G31 over 2160 hours at room temperature. Results showed that stain- less steel 304 had the lowest corrosion rate, followed by carbon steel SA 516 Gr.70 and brass. However, brass led to fuel degradation, notably in cleanliness, water content, and oxidation stability, making it unsuitable for storing diesel-biodiesel and diesel-biodiesel-HVO blends. HVO positively influenced bio- diesel-diesel blends, resembling diesel fuel and reducing total acid number and water content, thus low- ering corrosion rates of metals.
- KEYWORDs : Corrosion rate, Corrosion, Immersion, Biodiesel, HVO
- AUTHORs : Yayan Heryana†, Ade Pamungkas, Romelan Romelan, Maharani Dewi Solikhah, Matheofani, Bina Restituta Barus, Cahyo Setyo Wibowo, Faqih Supriyadi, Arfie Thahar, Edi Wibowo, and Soni Solistia Wirawan†
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Page : 365 - 373
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- Enhancing the Durability and Surface Properties of Ceramic-Glass via DLC Coating Method
- The purpose of this study was to investigate how diamond-like carbon (DLC) coatings could improve ceramic-glass durability and surface property. Ceramic-glass is valued for its aesthetic appeal. However, it is brittle and easily damaged. To address this issue, we looked into the use of DLC coatings known for their high hardness and low friction properties. Starting with cleaning the surface with linear ion guns to remove any impurities, a buffer layer was applied to enhance the adhesion of coatings. The DLC layer was deposited using unbalanced magnetron (UBM) sputtering, which maximized the deposition efficiency by controlling magnetic fields. Results demonstrated a significant improvement in mechanical properties of ceramic glass, with DLC-coated surfaces achieved a friction coefficient close to zero, a surface hardness of 22 GPa, and an adhesion strength exceeding 30 N. These findings confirm that DLC coatings can sub- stantially increase the durability and extend the service life of ceramic glass, making them a promising solution for enhancing performances of high-cost brittle materials.
- KEYWORDs : DLC, Wear resistance, Ceramic-glass, Plasma coating, Durability, Surface property
- AUTHORs : Jae-Un Kim, Byeong-Seok Lim, Byung-Woo Ahn, Young-Shin Yun, and Han-Cheol Choe†
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Page : 374 - 385
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- Non-Oxidizing Water Quench to Tailor UHSS for Excellent Zinc Wettability
- Recently, Fives Stein has developed a non-oxidizing wet cooling process dedicated to high strength steel quenching in continuous galvanizing lines to freeze desired bainite and martensite phases, triggering Tata Steel R&D to collaborate in an innovative project together with Fives Stein. They have demonstrated that this promising technology could improve metallurgy and coatability. This technology can be implemented for galvanizing 3rd generation Advanced High Strength Steel (AHSS) / Ultra High Strength Steel (UHSS) grades of Tata Steel. The pickling effect of wet cooling agent (water containing an acid) on steel surface after annealing prior to dipping into the Zn bath according to the wet cooling concept developed by Fives
Stein was assessed by a metallurgy driven set of experiments on a Non-Oxidizing-Water-Quench (NOWQ) cooling test bench simulation. Selected samples were further preheated to required temperature in 5%H /N 22 and subsequently dipped in liquid zinc by a hot dip zinc simulator HDAS (Heat to Coat heated, i.e., with- out annealing). Results of experiments along with X-ray Photoelectron Spectroscopy (XPS)/Glow Dis- charge Optical Emission Spectroscopy (GDOES) analyses demonstrated that the NOWQ technology significantly improved pickling efficiency of Mn, Si, and Al selective oxides to secure good Zn wetting of exposed metallic strip surface. - KEYWORDs : Non-Oxidizing-Water-Quench, Galvanizing, Wettability, AHSS
- AUTHORs : Cornelia Ionescu†, Peter Beentjes, Erdni Batyrev, S?bastien Lemaire, and Xavier Cluzel
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Page : 383 - 392
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- Modifying the τ5c-Al Fe Si (+Zn) Intermetallic Phase by Adding Vanadium into 55%Al-Zn Coating Alloy
- The presence of transition metals V, Cr or Mn in a 55%Al-Zn based coating metal can modify the equilibrium intermetallic phase, τ5c, by diffusion of transition metals and substituting for iron in the τ5c phase. We experimentally confirmed the modification of the IMC phase using various analytical techniques to charac-
terize IMC phases. Experimental results confirmed the formation of a modified τ5c-Al20 (Fe,V) Si (+Zn) intermetallic phase. The modified IMC phase showed periodic repeating layers with varying concentrations of V while still maintaining a constant (Fe+V)/Fe ratio within the homogeneity range of Fe in the equilibrium IMC phase.
We proposed a reaction-diffusion mechanism for forming a modified IMC phase and a periodic layered structure. The initial reaction of the steel strip resulted in the formation of Fe4Al13 IMC phase. Al, Si, and Zn diffused and reacted with Fe4Al13 to form the equilibrium bcc phase, τ5c. The Fe Al phase was consumed in the reaction, followed by diffusion of V into the newly formed phase by substitution of Fe by V, resulting in formation of the modified IMC phase. At 600 oC, the τ5c phase could dissolve up to 4.13 wt% (2.73 at.%) V without changing its overall bcc crystal structure. - KEYWORDs : Modified IMC, τ5c-Al Fe Si (+Zn), θ-Fe Al , Periodic-layered-structure formation, Newton’s Cradle
- AUTHORs : Nega Setargew†, Simon Correnti, Daniel Parker, Daniel McLachlan, and Dongdong Qu
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Page : 393 - 401
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- Formation Mechanism of Freckles on Zn-Al-Mg Coatings and their Influence on Processing Properties
- Zn-Al-Mg hot-dip-galvanized steel sheets exhibit some specific surface phenomena that have not been observed on GI coatings and have only been published to a limited extent. One visually very striking opti- cal appearance has been discussed in the literature under the names “freckles” and “dark spots.” However, only a rough formation mechanism has been described to date. Brisberger et al. found foreign particles in the center of the defect that could be considered to be a nucleation seed for a freckle. However, the influ- ence of these occurrences on processing properties has not yet been described. For more detailed infor- mation on the formation and cause of freckles, metallographic examinations and laboratory trials were carried out in a hot-dip galvanizing simulator to gain a fundamental understanding of the formation mech- anism. Topography and processing properties, such as phosphatability, paint appearance, forming proper- ties, and corrosion resistance, were assessed by various methods. Freckles exhibited locally altered crystallization due to a foreign particle, which has an impact on the Zn-Al-Mg coating itself as well as its complex microstructure. New findings on the formation mechanism were obtained from investigations with our hot-dip simulator, which showed possibilities for controlling these surface phenomena in an industrial environment.
- KEYWORDs : Zn-Al-Mg-coating, Coating defects, Freckles, Dark spots, Formation mechanism
- AUTHORs : Nils K?pper , Friedrich Luther and Thomas Koll
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Page : 402 - 409
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- Application of Automotive Closure Parts with Multi-Material Design Concept
- The automotive industry is changing rapidly with the electrification of vehicle powertrains. Many EV plat- forms have emerged, and the safety issues of battery-pack structures are being studied. The goal of vehicle design is a reasonable compromise between weight reduction and vehicle cost without decreasing vehicle performance or safety. Reducing the impact on global warming is another concern. Automotive industries are making efforts to confront this situation, one of which is using multi-material structures for vehicle bodies. Automotive closure parts account for more than 15% of the total vehicle body weight and have many different components. Therefore, efforts have been made to optimize the structure and material to reduce weight. However, applying different materials to automotive closure parts presents several techni- cal challenges. The combination of dissimilar materials is vulnerable to corrosion, and distortion may occur after the painting process due to the different thermal responses of the materials. From a manufac- turing perspective, the use of multi-materials can cause problems in the production line (process confor- mity). Thus, adaptive solutions to produce closure parts made of multi-materials are needed. This study addressed the design of multi-material closure parts and related manufacturing process issues, such as forming, assembling, corrosion resistance, and dimensional accuracy.
- KEYWORDs : Multi-material structure, Automotive closure, Lightweight design, Manufacturing technology, Life cycle analysis
- AUTHORs : Kanghwan Ahn, Kyunghwan Chung, Min Hong Seo , Gisuk Chung, and Yeonsik Kang
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Page : 410 - 415
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- Effect of Halide Ions on Hydrogen Entry Efficiency into Steel Sheet
- In this study, hydrogen permeation currents were investigated in hydrogen permeation tests for NaCl solu- tions at different concentrations to clarify the effect of chloride ion on hydrogen entry into the steel sheet. Hydrogen permeation currents for bromide and iodide ions were also investigated in the same test to deter- mine the effect of halide ion species on hydrogen entry. The amount of hydrogen entry increased with increasing chloride ion concentration in hydrogen permeation tests due to an increase in the amount of chloride ions adsorbed on the steel sheet surface, which prevented hydrogen atoms from bonding with each other. It was also found that hydrogen entry was higher in bromide and iodide ion environments than in the chloride ion environment. According to the HSAB rule, bromide and iodide ions are considered to have stronger adsorption with the steel sheet surface than chloride ions, preventing bonding between hydrogen atoms more than chloride ions.
- KEYWORDs : Hydrogen embrittlement, Hydrogen entry, Hydrogen permeation tests, Chloride ion, Halide ions
- AUTHORs : Hiroki Kawanami†, Takehiro Takahashi, and Tomohiko Omura
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