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Page : 444 - 452
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- Cathodic Protection Performance of ICCP System applied to Floating Offshore Reinforced Concrete Structure
- Reinforced concrete structures in marine environments frequently experience premature deterioration due to corrosion, particularly of the steel reinforcement, which is a leading cause of degradation in these struc- tures, including bridges and marine airports. In recent years, developed countries have increasingly turned to offshore spaces—such as floating wind farms, floating solar power plants, and floating waste treatment facilities—for infrastructure development, driven by a shortage of available urban land. This trend is also observable in our country, where, despite being surrounded by the sea on three sides, usable land in urban centers is extremely limited. To mitigate corrosion in reinforced concrete structures, various cathodic pro- tection methods are employed, including sacrificial anode cathodic protection (SACP) and impressed cur- rent cathodic protection (ICCP). Among these, ICCP is the preferred method due to the high electrical resistivity of concrete. In this study, we applied an ICCP system powered by self-generated energy sources—such as wind power, solar power, and ocean thermal energy—to floating reinforced concrete off- shore structures. The performance of the ICCP system was assessed by measuring the cathodic protection current, cathodic protection potential, and depolarization potential.
- KEYWORDs : Corrosion, ICCP System, SACP System, Potential, Resistivity
- AUTHORs : Du-Hyeong Lee and Jin-A Jeong†
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Page : 453 - 469
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- Effect of Sulfuric Acid Concentration on Corrosion Between Au or Cu Bonding Wire and Pads for Semiconductor Packaging
- Wire bonding is still prevalent in conventional semiconductor packaging. However, degradation can occurduring use or storage due to factors such as humidity, acidity, and ionic contamination. This study investigates the corrosion behavior of packaging structures with Al and Au bond pads combined with Au and Cu wires in sulfate-based environments. Electrochemical evaluations, including individual polarization and galvanic tests, were performed in de-aerated 1% Na2SO4 solutions with varying H2SO4 concentrations. Tafel analysis provided data on corrosion potential (Ecorr), corrosion current density (icorr), galvanic potential/current density, and total charge. Additionally, a Temperature-Humidity Test (85 oC/85% RH) was conducted under 1% Na2SO4 with either 0% or 1% H2SO4 conditions, using PCB unit specimens that featured a 1st ball bond on an Al pad and a 2nd stitch bond on an Au pad, bonded with either Au or Cu wires. The surface morphology and elemental distribution were qualitatively analyzed before and after exposure using a 3D optical microscope and FE-SEM/EDS.
- KEYWORDs : Packaging, Au or Cu wire bonding, Al or Au pad, Corrosion, Temperature-Humidity Test
- AUTHORs : Sang-Shin Lee, Young-Ran Yoo, Seung-Heon Choi, Jae-Hyeok Choi, Hyeun-Sik Jang, Young-Cheon Kim†, and Young-Sik Kim
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Page : 470 - 477
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- 반도체 공정용 Ni-Cr-Mo계 합금의 전해연마에서 전해액 조성이 표면 품질에 미치는 영향
- This study investigated how electrolyte composition affects surface roughness during the electropolishing of Ni-Cr-Mo alloys. Mixtures of phosphoric acid, sulfuric acid, and water in ratios ranging from 6:3:1 to 8:1:1 were tested at 50 oC and 3.5 V for 20 minutes. The 7:2:1 ratio produced the lowest surface rough- ness, meeting semiconductor specifications. Surface observations revealed uniform dissolution with min- imal bubble traces. An inverse correlation between weight loss and conductivity with Ra suggested that smoothness is governed by uniform, rather than excessive, dissolution. ICP-OES analysis identified nickel and chromium as the primary elements dissolving from the alloy, contributing to surface leveling, while molybdenum enhanced corrosion resistance. Conversely, significant amounts of iron were detected, which were attributed to contamination from the experimental jig rather than from the alloy's primary dissolu- tion. Copper was also found to originate from counter-electrode dissolution. These results indicate that bath contamination from the fixtures (jig and electrode) is a critical process variable. Overall, the 7:2:1 electrolyte effectively balanced the viscous film-forming properties of phosphoric acid with the ionic con- ductivity of sulfuric acid, facilitating stable electrochemical dissolution and achieving a defect-free finish.
- KEYWORDs : Electropolishing, Ni-Cr-Mo alloy, Surface roughness, Electrolyte composition, Dissolution behavior
- AUTHORs : 양현석 · 정우철 · 한덕현 · 최광수 · 성열주 · 공만식†
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Page : 478 - 492
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- Al-Si 도금강의 Mg 및 Zn 함량 변화에 따른 부식 거동 조사
- This study aimed to enhance the corrosion resistance of Al–10Si-based plated steel by incorporating Mg and Zn—elements known for their low corrosion potentials—into the plating layer. We analyzed the effects of varying the content of these elements on both the microstructure and corrosion behavior. Using a Central Composite Design method, we developed nine plating compositions that combined Zn (0, 7.5, 15 wt%) and Mg (0, 2.5, 5 wt%). We evaluated the electrochemical properties of the plating layers through potentiodynamic polarization tests in a 3.5 wt% NaCl aqueous solution and examined the microstructures before and after corrosion using optical microscopy and SEM-EDS. The results of the potentiodynamic polarization tests revealed corrosion potentials ranging from -0.93 V to -0.56 V. Corrosion rates increased with Mg content, ranging from 2.36 × 10-6 A/cm to 2.9 × 10-5 A/cm . Statistical analysis indicated that Zn content primarily influenced corrosion potential, while Mg content affected the corrosion rate. Cross-sectional observations post-corrosion testing confirmed micro-galvanic corrosion behavior, characterized by the selective dissolution of eutectic Al-Si phases surrounding Si-rich phases within the plating layer.
- KEYWORDs : Corrosion, Al-Si Coating, Zn, Mg
- AUTHORs : 이수진 · 진주연 · 왕은찬 · 최윤일 · 장희진†
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Page : 493 - 504
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- 해양 구조물용 고장력강의 해수 내 정전위방식실험에 따른 전기화학적 거동 및 표면특성 연구
- High-strength steel used in marine structures is consistently subjected to harsh environments, influenced by factors such as salinity and flow velocity in seawater. To solve corrosion, impressed current cathodic pro- tection systems are employed. This investigation compares and analyzes the electrochemical behavior and surface characteristics of AH32 high-strength steel under various corrosion protection conditions in a sea- water environment. To achieve this, cathodic polarization and potentiostatic polarization experiments were conducted to assess the effects of applied potential on corrosion characteristics and surface conditions. When a potential between -0.80 V and -0.95 V (vs. Ag/AgCl, 3.3 M KCl) was applied, low current density is observed. In addition, concentration polarizationby reduction reaction occurred without any observed surface damage. Thus, this potential range was determined to be an excellent protection condition. Con- versely, at an applied potential of -1.1 V or lower, surface roughness increased significantly due to surface damage from excessive hydrogen generation. Notably, numerous interparticle peelings and microcracks were detected between -1.2 V and -1.3 V.
- KEYWORDs : Cathodic protection, High-strength steel, Electrochemical behavior, Hydrogen-induced degradation, Marine corrosion
- AUTHORs : 신동호 · 황현규 · 김성종†
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Page : 505 - 514
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- 소형선박 프로펠러용 6000계열 알루미늄 합금의 양극산화시간에 따른 캐비테이션 -침식과 부식의 복합거동
- Al-Mg-Si aluminum alloys used in small ship propellers are subjected to a challenging environment where cavitation-erosion and corrosion occur simultaneously in seawater. This study explored anodized aluminum alloy as an alternative technology. We conducted indentation tests and a hybrid experiment combining electrochemical and cavitation-erosion assessments. The indentation results showed that anodized specimens treated for 10, 20 and 40 minutes had significant hardness increases of 208.282, 336.74 and 369.276 Hv, respectively, compared to the base material's hardness of 94.9 Hv, with a notable suppression of creep behavior. In the hybrid experiment, the anodized specimen treated for 10 minutes demonstrated a current density increase, delaying in the range of -0.8775 V to -0.7966 V, and exhibited the lowest corrosion current density of 2.55 μA/cm . Following this experiment, the anodized speciment treated for 10 minutes also showed the lowest weight loss (40.9 mg), surface roughness (14.4 μm) and maximum dam- age depth (93.8 μm). Conversely, the specimen anodized for 40 minutes exhibited higher hardness than the 10-minute specimen, but showed an increased tendency for cracks and damage due to reduced toughness.
- KEYWORDs : Aluminum, Anodizing, Indentation, Corrosion, Cavitation-erosion
- AUTHORs : 신동호 · 황현규 · 김성종†
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Page : 515 - 526
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- 해양 구조물용 고장력강의 해수 내 저변형률 인장속도에 따른 응력부식균열 특성 연구
- This research explores the stress corrosion cracking (SCC) behavior of AH32 high-strength steel under slow strain rates by comparing its performance in air and seawater environments. Optical microscope observations revealed that the high-strength steel has a ferrite–pearlite microstructure, with pearlite concentrated in specific regions. This microstructural inhomogeneity likely influences the formation of micro-galvanic cells and areas of stress concentration, contributing to the onset of SCC. Slow strain rate tests were performed at rates of 0.004, 0.001, and 0.00075 mm/min. The results showed that in seawater, as the strain rate decreased, there were greater reductions in elongation, time to fracture and absorbed energy. Fracture surface analysis revealed cleavage planes under seawater conditions, indicating a brittle fracture behavior of the material. In contrast, specimens tested in air exhibited ductile fracture characteristics, such as dimples and shear lips. These findings suggest that the seawater environment significantly facilitates the initiation and propagation of SCC in high-strength steel.
- KEYWORDs : High-strength steel, Slow strain rate test, Stress corrosion cracking, Seawater, Corrosion
- AUTHORs : 신동호 · 황현규 · 김성종†
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Page : 527 - 538
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- 1 wt% Cr 첨가 페라이트계 강 내 미량 첨가된 합금원소 (C, V, Mo)가 CO2 포화 산성 수용액 내 부식 거동에 미치는 영향
- This study examined the effect of micro-alloying elements (C, V, and Mo) on the corrosion behavior of 1Cr-containing ferritic steel in a CO2-saturated acidic aqueous solution. A variety of experimental methods were employed, including microstructural analyses, electrochemical measurements, and surface examinations. The findings revealed that an increased addition of carbon (C) to this alloy system led to a higher fraction of coarse Fe C and M C , which limited chromium (Cr) enrichment in the inner corrosion scale and caused the FeCO3 crystals on the outer surface to coarsen. These changes resulted in a greater sus- ceptibility to long-term corrosion. In contrast, the addition of vanadium (V) markedly enhanced Cr enrich- ment in the inner layer and refined the FeCO3 crystals on the outer layer of the corrosion scale, leading to improved long-term corrosion resistance. Molybdenum (Mo) also contributed to enhanced corrosion resis- tance, similar to V, but during the early stages of corrosion, it exhibited much higher dissolution rates and showed a limited ability to form protective FeCO3 layers under acidic conditions, which may impede the full realization of its corrosionresistant benefits.
- KEYWORDs : C, V, Mo, CO corrosion, Steel
- AUTHORs : 윤성준 · 윤덕빈 · 방혜린 · 김완근 · 김성진†
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Page : 539 - 557
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- Elucidation of Corrosion Mechanism in a Simulated Potable Water of 304 stainless steel for Water Storage Tank
- Drinking water storage tanks are essential for maintaining water quality in distribution systems, and their stability is crucial. STS 304 stainless steel, known for its excellent corrosion resistance, is commonly used in water supply facilities and storage tanks. However, localized corrosion has been observed in STS 304 tanks, likely due to local enrichment of chloride (Cl-) or residual chlorine (OCl-) ions caused by evaporation and condensation. This study evaluated the corrosion behavior of STS 304 base metal and weld metal in simulated potable water containing 50 ppm, 200 ppm, or 400 ppm Cl- and 2 ppm, 4 ppm, or 8 ppm OCl- at temperatures of 20oC, 35 oC, and 50 oC. To assess corrosion resistance, we conducted cyclic polarization, open-circuit potential (OCP) measurements, and electrochemical impedance spectroscopy (EIS). While increases in Cl and OCl- ions had minimal impact on pitting and protection potentials, higher temperatures led to a decrease in pitting potential. The addition of OCl caused a rapid increase in OCP to a level between the protection and pitting potentials, indicating that the corrosion observed in 304 tanks is linked to the potential-raising effect of OCl- ion addition.
- KEYWORDs : Potable water tanks, 304 Stainless steel, Hypochlorite (OCl ), Pitting potential, Protection – potential
- AUTHORs : Jae-Hyeok Choi, Seung-Heon Choi, Sang-Shin Lee, Young-Ran Yoo, Hyun-Hak Cho, Young-Cheon Kim†, and Young-Sik Kim
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Page : 558 - 566
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- DRM 진단기술을 이용한 열수송관의 절연체결함 진단사례
- The corrosion control methods for buried pipelines typically involve insulation techniques such as coating application, supplemented by cathodic protection. Non-destructive survey technologies for detecting defects in the insulation of buried pipelines are essential for safety management. Existing ground-based measurement technologies are influenced by soil parameters, making it challenging to detect defects in deeper sections of the pipeline and in areas such as waterways and roads. A new survey technology, Differential Reflectometry Mapping (DRM), utilizes the reflection measurement method to directly assess the pipeline itself. Due to its minimal influencing parameters, DRM maintains high sensitivity, allowing for the detection of early corrosion defects and the ability to assess the extent of these defects. DRM surveys and field verification were conducted on heat pipes in an urban environment. This method proved effective for measuring buried pipelines, which are difficult to assess with existing ground-based technologies, and field verification indicated an accuracy of approximately ±1meter. Additionally, the size of the pipeline defects was quantified, enabling effective prioritization of the issues.
- KEYWORDs : DRM technology, Heat transport pipe, Buried pipeline, Coating detection, Insulator detection
- AUTHORs : 손대홍† · 이상혁 · 배근호 · 이해용
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