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Page : 327 - 346
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- Advanced Bipolar Model Based on the Semiconductive Properties of the Passive Film in Stainless Steel
- This study evaluated the electrochemical and semiconductive properties of passive films on austenitic stainless steels with varying pitting resistance equivalent (PRE) values in deaerated HCl solutions. The electrochemical analysis indicated that higher PRE values resulted in a lower passive current density (ip) and an increased polarization resistance (Rp). XPS depth profiling showed that the passive film had a bilayer structure: the inner layer primarily consisted of Cr2O3/ Cr(OH)3, while the outer layer was enriched with oxyanion species such as CrO42− and MoO42−. As PRE increased, the proportion of Cr2O3 in the inner layer rose, while the outer layer had a higher concentration of oxyanions. These alterations led to a simul- taneous increase in both p-type and n-type slopes. To quantify this effect, the ‘Bipolar Index (|p-type slope| + |n-type slope|)’ was applied, and an advanced bipolar model of the passive film was proposed. An increase in the bipolar index was associated with a decrease in passive current density (ip), an increase in polarization resistance (Rp), and a reduction in the total defect density within the passive film.
- KEYWORDs : Stainless steel, Passive film, PRE, Mott-Schottky, Advanced bipolar model
- AUTHORs : Seung-Heon Choi, Young-Ran Yoo, Young-Cheon Kim†, and Young-Sik Kim
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Page : 347 - 359
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- Improvement of the Reliability of Pipelines Buried in Soil through Real-time Monitoring and Control for Cathodic Protection and Coating Defect Detection
- Buried pipelines face corrosion risks during long-term operation in soil environments, primarily due to coating defects or degradation of cathodic protection performance. To mitigate these issues, it is crucial to accurately assess the condition of cathodic protection and promptly identify any coating defects. This study investigated the cathodic protection status at domestic power plant sites and established a mock-up facility for real-time assessments of cathodic protection and coating defect detection. This was achieved using on- off potential measurements, Close Interval Potential Survey (CIPS), and Direct Current Voltage Gradient (DCVG) techniques. The findings revealed that the cathodic protection condition at existing sites was locally inadequate. In contrast, the mock-up facility allowed for continuous monitoring of on-off potential variations, and real-time CIPS and DCVG measurements effectively identified potential changes and sig- nal reversals at the sites of intentionally introduced coating defects, aligning closely with their actual loca- tions. These results demonstrate that implementing real-time monitoring and defect detection systems for buried pipelines in soil can significantly improve the reliability of cathodic protection management.
- KEYWORDs : Buried pipe, Cathodic protection, CIPS, DCVG, Real-time defect detection
- AUTHORs : Seung-Heon Choi, Bu-Taek Lim, Ki-Tae Kim, Dae-Young Lee, Jae-Hyeok Choi, Sang-Shin Lee, Young-Ran Yoo, Young-Cheon Kim†, and Young-Sik Kim
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Page : 360 - 367
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- Thermal Dissipating Composite Coated PosMAC Steel Sheets for Building Integrated Photovoltaic Module
- As an eco-friendly energy source, building-integrated photovoltaic (BIPV) modules that incorporate build- ing materials and flexible solar cells are rapidly advancing. However, semiconductor-based solar cells often experience reduced power generation efficiency due to rising summer temperatures. To address this issue, thermal-dissipating composite-coated PosMAC steels with excellent thermal radiation properties have been developed as backsheet materials for BIPV modules. These steels are manufactured by applying a highly durable coating with both excellent thermal radiation and corrosion resistance characteristics on both sides. The front side, where the solar module is attached, is treated with a black-colored solution that includes high-crosslinking polyester resin and thermal conductive pigments to ensure corrosion resistance for over 20 years. The rear side is coated with a dispersive polyester polymer resin solution containing thermal conductive pigments with significant anisotropic properties, which greatly enhances heat dissipa- tion by forming fine wrinkles on the surface to maximize surface area, achieved by adjusting the content of the hardening catalyst. This paper describes the thermal characteristics evaluation of the thermal-dissipat- ing composite coated on PosMAC steels, as well as the fabrication of two types of BIPV roof modules combined with CIGS solar cells.
- KEYWORDs : BIPV, Building integrated photovoltaic, PosMAC, Thermal dissipating steels, Thermal Emissivity
- AUTHORs : Du-Hwan Jo† , Peter J. Toonssen, and Kyunghoon Nam
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Page : 368 - 375
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- Inline Measurement of Surface Roughness and Oil Film Thickness – Smart Press Shop Uses Decisive Parameter Data in Galvanized Strip Forming
- Surface roughness and oiling condition of incoming coils are two critical quality-parameters determining the friction between blank and deep-drawing die in galvanized strip forming, in particular the flow behaviour of the blank pressed around die edges. AMEPA commissioned a unique tribological system at Smart Press Shop in Halle/Saale/Germany, a Joint Venture between Porsche and Schuler Pressen. The inline system measures surface roughness and oil film of galvanized strips for body in white parts. It is integrated into the Schuler Track & Trace system. Press parameters are adjusted to each coil processed based on inline measurements, ensuring perfect forming. An inline Surface Roughness Measurement System (SRM system) uses a light-section method. The OFM system measures reflection and absorption of infrared light projected onto the strip and calculates the oil film in g/m2. If values are not within tolerance,
systems trigger a warning for operators to take immediate action. A key aspect is the system’s capability to adjust press line parameters so that parts otherwise graded as out-of-spec could leave the press line as OK products. Thus, a poorly oiled strip that normally would fail in the forming process can be turned into a “good” strip by re-oiling. - KEYWORDs : Galvanized strip, Roughness, Oil film, Press shop, Track & Trace
- AUTHORs : Andreas Gebele, Martin Fieweger†, Ansgar Berlekamp, and Dr.-Ing. Wolfgang Bilstein
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Page : 376 - 384
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- 황산 수용액 내 듀플렉스 스테인리스강 (UNS S32205)의 부식거동에 미치는 용접프로세스 및 필거압연 공정의 영향
- This study investigated the corrosion behavior of duplex stainless steel (S32205) fabricated using plasma arc welding (PAW) and laser beam welding (LBW), followed by post-weld heat treatment (PWHT) and pilgering processes. We evaluated the impact of sulfuric acid concentrations (5% and 50%) on corrosion resistance using potentiodynamic polarization, immersion tests, and critical pitting temperature (CPT) measurements. Microstruc- tural analysis showed that LBW produced narrower, deeper welds with finer grains and significantly lower oxide inclusion fractions compared to PAW. In 50% sulfuric acid, LBW demonstrated lower passive current densities and more stable passivation, attributed to its reduced inclusion content and suppression of local anodic dissolution. PWHT restored the δ/γ phase balance to approximately 50:50, enhancing corrosion resistance, while pilgering introduced high residual stress and caused a γ→ε transformation, resulting in decreased CPT and increased local- ized attack. Weight loss in 5% sulfuric acid was negligible across all conditions, whereas in 50% acid, it increased significantly for pilgered samples. These findings suggest that LBW, particularly with optimized PWHT, provides superior corrosion performance and strong potential for applications in heat recovery steam generator (HRSG) components of combined-cycle power plants.
- KEYWORDs : Combined cycle power plant, Heat recovery steam generator (HRSG), Duplex stainless steel, Sulfuric acid corrosion, Laser beam welding
- AUTHORs : 장유성 · 백규빈 · 박진성 · 홍승갑 · 김성진†
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Page : 385 - 392
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- 오스테나이트계 18Mn강의 인공해수 내 부식 및 마모 거동
- This study examines the corrosion–wear behavior of microalloyed high-Mn steels and carbon steel in artificial seawater, focusing on the role of Cr. Microstructural characterization, electrochemical testing, weight-loss measurements, and molecular dynamics (MD) simulations were conducted. The Cr-containing 18Mn steel demonstrated superior electrochemical stability during the corrosion–wear process owing to the formation of Cr-rich oxides (e.g., Cr2O3, FexCr3-xO4)and their rapid reformation after mechanical damage from repeated wear. Consequently, it exhibited the lowest corrosion current density and the highest polar- ization resistance over 14 days of testing. In contrast, conventional 18Mn steel showed the greatest elec- trochemical activity and weight loss, exceeding those of carbon steel, due to accelerated Mn dissolution and repeated wear by coarse V-bearing carbides that degraded surface protection. MD simulations further revealed that, under aqueous conditions, Fe–Mn alloy system undergo greater atomic-scale surface dis- ruption than Fe–Cr alloy system, hindering the formation of stable interfacial oxides. These results elu- cidate the corrosion–wear mechanism and propose a viable alloying strategy to enhance the durability of offshore structural components exposed to cyclic wear and seawater environments.
- KEYWORDs : Artificial seawater, Corrosion, Cr, High Mn steel, Wear
- AUTHORs : 유재민 · 박진성 · 이상철 · 김성진†
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Page : 393 - 401
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- 해양환경에서 Al-Mg-Si 알루미늄 합금의 부식 및 캐비테이션 -침식 저항성에 미치는 양극산화시간의 영향
- In this investigation, anodizing of aluminum alloy was conducted at a current density of 20 mA/cm in a 10 vol.% sulfuric acid solution at 10 oC for durations of 10, 20, and 40 minutes. The electrochemical char- acteristics and cavitation-erosion behavior of the anodized specimens in natural seawater were examined in relation to anodizing time. In a static seawater environment, results from the potentiodynamic polarization experiments indicated that the corrosion current density decreased with longer anodizing times. This improvement in corrosion resistance is attributed to the increasing thickness of the oxide film, which slows or blocks the rate at which chloride ions—corrosive agents in seawater—reach the base material. The cav- itation-erosion experiment revealed that the maximum damage depth of the specimen anodized for 10 min- utes was reduced by 63.903 m compared to the uncoated base material. However, while the thickness of the oxide film increased for the specimen anodized for 40 minutes, its higher brittleness diminished the toughness necessary to prevent crack formation and propagation, ultimately weakening its resistance to cavitation and erosion.
- KEYWORDs : Aluminum, Propeller, Anodizing, Corrosion, Cavitation-erosion
- AUTHORs : 황현규 · 신동호 · 김성종†
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Page : 402 - 410
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- GTD-111의 고온용융염부식에 미치는 염 도포 및 세척 조건의 영향
- Hot corrosion behavior of GTD-111 Ni-based superalloy was systematically evaluated by applying various salt deposition methods and cleaning protocols. Corrosion tests were conducted at 700 °C using different salt application techniques, including dipping and brushing with or without pre-test drying. Cleaning pro- cedures involved either ultrasonication or soaking the superalloy in still water at various intervals during cyclic exposure. Corrosion behavior of the GTD-111 Ni-based superalloy was evaluated through weight change measurements and microstructural analyses. Results showed that an increase in salt loading led to an accelerated corrosion rate and that ultrasonic cleaning markedly accelerated mass loss. Among different procedures tested in this work, drying the specimen coated with a salt solution before testing and per- forming ultrasonic cleaning every four cycles minimized data variations and provided more consistent cor- rosion behavior. XRD and SEM-EDS analyses identified main corrosion products as NiO, NiAl₂O₄, Cr₂O₃, Al₂O₃, and NiS. Spallation primarily occurred around the Cr oxide scale.
- KEYWORDs : Hot corrosion, Ni-based superalloy, Cyclic corrosion test, Molten salt, Experimental procedure
- AUTHORs : 장희진† · 김창기 · 서성문 · 정희원 · 유영수
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Page : 411 - 433
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- Eco-Friendly Corrosion Inhibition of Mild Steel in 1 M HCl Using Trametes versicolor (Turkey Tail Mushroom) Extracts: Experimental and Theoretical Insights
- In pursuit of greener corrosion control, this study evaluates Trametes versicolor (Turkey Tail Mushroom) extract as a corrosion inhibitor for mild steel in 1 M HCl. Using experimental and theoretical approaches, the extract achieved up to 92.1% inhibition efficiency at 800 mg/L, though efficiency declined with higher temperatures, suggesting predominantly physical adsorption with possible chemisorption. GC-MS/MS and FTIR analyses revealed various bioactive compounds—mainly flavonoids and polyphenols—containing functional groups like hydroxyl, carbonyl, and amine that promote protective film formation on the metal surface. UV-Vis spectroscopy confirmed iron-inhibitor complex formation, indicating chemical interac- tions at the interface. To support these results, DFT, MD, and MC simulations provided molecular-level insights into adsorption behavior, highlighting myricetin and rutin as key compounds with strong binding affinities and favorable electronic properties. A QSAR model with 22 molecular descriptors was devel- oped to predict adsorption energies, identifying frontier orbital energies and surface area as major factors influencing inhibitor performance. These findings demonstrate the potential of T. versicolor extract as an eco-friendly corrosion inhibitor and offer valuable molecular insights for designing bio-based corrosion control strategies.
- KEYWORDs : Trametes versicolor, Corrosion inhibition, Phytochemicals, Molecular dynamics simulations, Sustainable inhibitors
- AUTHORs : Qëndrim Ramshaj, Adelina Halili, Veprim Thaçi, Jeton Halili, Valbonë Mehmeti, Behar Baxhaku, Makfire Sadiku, Ilir Mazreku, Arianit Reka, and Avni Berisha†
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Page : 434 - 443
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- 24 Years of Galvanized Autobody Partnership – Highlights and Prospects
- Automotive industry requirements continue to drive advancements in the hot-dip galvanizing (HDG) pro- cess. While zinc-coated advanced high-strength steels (AHSS) are routinely produced, further improve- ments are still necessary. To enhance control over AHSS surface uniformity during annealing, computational tools are being developed to predict selective oxidation of alloy elements and surface decarburization. Press- hardened steels (PHS) are increasingly being used to optimize steel utilization in automotive body struc- tures, and advancements in utilizing zinc-coated grades to improve their durability are ongoing. This doc- ument describes the effects of processing both galvannealed (GA) and galvanizing (GI) coated precursor grades. A significant cause of HDG process deviations is inaccuracies in pyrometric temperature mea- surements in the pretreatment furnace. Research on the effects of dewpoints and temperatures on emis- sivity has been conducted, leading to the development of a predictive model. The contributions of the Galvanized Autobody Partnership (GAP) program—a collaboration between the steel and zinc industries and their suppliers—to these improvements are discussed, along with implications for further technical developments.
- KEYWORDs : Continuous Hot-dip Galvanizing, Surface Decarburization, Press Hardened Steel, Pyrome- try, Automotive Steel
- AUTHORs : A. P. Domingos and F. E. Goodwin†
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