본 연구는 수소 탱크를 고정하는 강재 볼트의 부식으로 인한 성능 저하 문제를 해결하기 위해 내부식성 복합재료로 알려진 Glass Fiber Reinforced Polymer (GFRP) 및 Carbon Fiber Reinforced Polymer (CFRP)를 활용한 앵커 시스템을 제안하고, 이를 지진 하 중 하에서의 안전성 평가를 통한 적용 타당성 검토를 수행하였다. 연구에서는 현장 조사를 통해 실제 사용 중인 수소 탱크의 설계 제 원을 확보한 후 이를 바탕으로 유한요소해석을 수행하였으며, AC 156 인공 지진파를 적용하여 FRP 앵커 볼트와 기존 강재 앵커의 성 능을 비교 분석하였다. 주요 분석 결과, FRP 앵커 볼트를 적용한 수소 탱크는 강재 앵커 볼트에 비해 고유 진동수가 21% 증가하여 구 조적 강성이 향상됨을 확인하였다. 또한, 가속도 응답 분석 결과 FRP 앵커 볼트는 상부 가속도를 감소시켜 지진 하중에 대한 저항성을 증진하는 것으로 나타났다. 응력 해석에서는 FRP 앵커 볼트가 강재 앵커 볼트에 비해 유효 응력이 약 91% 감소하여, 구조적 안전성이 크게 개선되었다. 그러나, FRP 앵커 볼트 적용 시 기초 콘크리트에 가해지는 쪼갬 인장 응력이 강재 앵커 대비 최대 3.5배 증가하는 것으로 나타났으며, 이에 따라 FRP 앵커 볼트 사용 시 기초 콘크리트의 보강이 필요할 것으로 사료된다. 이러한 연구 결과는 수치해석 에 국한된 결과로, 향후 실제 지진 하중을 모사한 실험적 검증이 필요하다. FRP 앵커 볼트의 적용 가능성은 향후 연구를 통해 광범위 하게 평가될 것이며, 이를 통해 수소 인프라의 내구성과 안전성을 더욱 강화할 수 있을 것으로 기대된다.

Super-duplex stainless steels are in great demand in various industrial fields such as chemical processing and seawater desalination due to their excellent pitting corrosion resistance. However, detrimental phases can easily form during fabrication, and even minor additions of alloying elements can significantly impact their microstructure and properties. This study investigated the effects Cu or Ti additions on a super-duplex stainless steel. First, the effects of annealing time at 950 °C on the microstructure and corrosion characteristics were investigated. It was found that as the annealing time increased, the fraction of sigma phase increased; however, the corrosion resistance in the electrochemical test using a 3.5 % NaCl electrolyte showed only a slight improvement. The microstructure of duplex stainless steel with added Cu or Ti did not differ significantly from that of the base steel. However, the overall corrosion resistance showed improvement, and in particular, an observed increase in pitting potential. Investigating the characteristics of the passive film on the alloy surface revealed that the stability of the passive film was higher in alloys with added Cu or Ti compared to the standard alloy. Among these, the alloy with Cu addition had the thickest film, while the Ti-added alloy had the highest Cr concentration and a film thickness greater than that of the standard alloy.

Recently, corrosion problems caused by quarantine disinfectant have occurred in the door panel of commercial trucks. As a way to solve this problem, a drain hole is being drilled in the door panel, and the door panel is being designed again for this purpose. Reinforcing parts such as frames or brackets for rigidity are attached to the inner and outer door panels, and spot welding is performed for assembly. X-rays and nugget diameter measurements of the welds were performed to confirm the results of performing according to various conditions for such spot welding. Through this study, it was confirmed that the pressing force had a greater effect on the welding quality than the amount of welding current.

국내 도로표지는 국토교통부에서 제정한 「도로표지 제작·설치 및 관리지침」을 토대로 설계와 시공이 이루어지고 있으며 문형식 과 편지식 도로표지 기초는 주로 역 T형 형식을 적용하고 있다. 기초 상단이 갓길 측은 성토 비탈면에, 중앙분리대 측은 포장 면에 위 치하여 기초 연결부가 고부식성 환경조건에 놓이게 된다. 이는 지주 및 앵커볼트에 부식이 쉽게 발생하고 장기적으로는 구조성능 저 하로 이어질 수 있는 사안이다. 아울러, 중앙분리대 측 문형식 도로표지 지주에는 방호 시설이 없는 상태로 차량 충돌 시 변형 또는 전도 위험과 2차 사고 발생 가능성 있다. 본 연구에서는 문형식과 편지식 도로표지 기초를 방호울타리 상단까지 높이는 방법으로 개선하였다. 풍하중에 의한 지주 휨모멘트 가 평균 18% 감소 되어 경제적인 설계가 가능하고 기초 연결부 환경조건이 개선되었다. 중앙분리대 측은 교통차단 등 특별한 조치 없 이도 상시 육안 점검이 가능하게 되어 유지관리 효율성이 증가하였고 방호성능 확보로 차량 충돌 시 지주 변형 또는 전도 위험이 해 소되었다. 결론적으로 기초 상단을 높임으로써 내구성, 유지관리 효율성 및 방호성능 향상을 기하면서도 경제적인 설계가 가능하게 되었다.

This study aims to propose a simplified equation for estimating the bond strength of corroded reinforcing bars. To this end, extensive parametric analyses were performed using the detailed analysis method presented in the authors’ previous study, where a wide range of critical variables were considered, such as compressive strength of concrete, net cover thickness, and reinforcing bar diameter. The sensitivity in bond strength of the corroded reinforcing bar according to each variable was evaluated. On this basis, a simplified formula for the bond strength of the corroded reinforcing bar was derived through regression analysis. The proposed equation was rigorously tested and verified using the bond test results of corroded reinforcing bars collected from the literature. The results confirmed that the proposed equation could estimate the bond strengths of specimens with better accuracy than the existing models, providing a reliable tool for engineers and researchers. In addition, the proposed equation was used to analyze the development length required for corroded tensile reinforcement to exert its yield strength, and it showed that the cover thickness of concrete must be at least four times the diameter of the reinforcing bar to achieve the yielding strength of reinforcing bar even at a corrosion degree of more than 5.0%.

국내 건축물에서는 노후한 철근콘크리트 구조물의 안전성이 중요한 문제로 대두되고 있다. 구조물 부분이나 전체의 무너짐으로 인해 경제적 손실을 초래할 수 있으며, 이는 주로 구성 재료의 내구성 결 함으로 인해 발생한다. 여러 노후화 인자 중 동결융해와 부식은 주요한 열화 요인으로 작용한다. 동결 지역의 구조물은 동결융해가 위험 요소로 작용할 수 있으며, 해양 구조물은 해수에 존재하는 염소이온 에 의해 부식될 수 있다. 이러한 문제를 해결하기 위해서는 복합 열화 작용과 철근콘크리트 부재의 성 능 저하 관계를 이해하는 것이 필요하다. 본 연구는 동결융해와 부식의 복합적 피해가 RC 보의 거동 에 미치는 영향을 실험적으로 조사하였다. 7개의 RC 보를 제작하여 각각 다른 수준의 열화 조건을 부여한 후 휨 시험을 실시하였다.

The current study explores the possibility of graphene as a protective layer on the zinc substrate through an optimized electrophoretic deposition process. Graphene has been synthesized from H2SO4, HNO3, and HClO4 solutions by an electrochemical exfoliation route. This method is known for providing a scalable and economical approach to the synthesis of graphene. The exfoliated graphene nano-sheets were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, UV–visible, and field emission scanning electron microscope to evaluate its properties. The three different synthesized forms of graphene nano-sheets were electrophoretically deposited onto Zn substrates at two different potentials. Scratch testing was employed to check the adhesion quality of the coatings. The corrosion behaviour of Zn and graphene-coated Zn substrates was studied in borate buffer and 3.5 wt% NaCl solutions through potentiodynamic polarization and electrochemical impedance spectroscopy. It

This study systematically investigated the efficacy of incorporating graphene/cerium hydroxide (GH) composite material into epoxy-modified polyurethane resin coatings for enhancing the corrosion resistance of Q690qE steel within polluted marine atmospheric conditions. The research encompassed a range of electrochemical assessments and analyses. Notably, the E/GH-0.3% coating displayed a substantially positive open-circuit potential (OCP) and prominently reduced corrosion current density, leading to annual corrosion rates of 2.72 mm/a following 25 days of immersion. Electrochemical impedance spectroscopy (EIS) elucidated the superiority of the E/GH-0.3% coating, characterized by the highest impedance modulus |Z| at 0.1 Hz, indicative of robust corrosion protection. Remarkably, the self-healing performance of E/GH-0.3% and E/ GH-0.5% coatings was evidenced by the formation of a composite passivation layer at scratch sites, particularly pronounced after 40 days of immersion. These findings underscore the promising potential of the GH composite as an effective corrosion inhibitor, holding significant promise for the advancement of protective coatings in harsh coastal industrial environments.

In this study, the physical properties and fracture characteristics according to the tensile load are evaluated on the materials of the polymeric filler and carbon fiber-based composite sleeve technique. The polymeric filler and the composite sleeve technique are applied to areas where the pipe body thickness is reduced due to corrosion in large-diameter water pipes. First, the tensile strength of the polymeric filler was 161.48~240.43 kgf/cm2, and the tensile strength of the polyurea polymeric filler was relatively higher than that of the epoxy. However, the tensile strength of the polymeric filler is relatively very low compared to ductile cast iron pipes(4,300 kgf/cm2<) or steel pipes(4,100 kgf/cm2). Second, the tensile strength of glass fiber, which is mainly used in composite sleeves, is 3,887.0 kgf/cm2, and that of carbon fiber is up to 5,922.5 kgf/cm2. The tensile strengths of glass and carbon fiber are higher than ductile cast iron pipe or steel pipe. Third, when reinforcing the hemispherical simulated corrosion shape of the ductile cast iron pipe and the steel pipe with a polymeric filler, there was an effect of increasing the ultimate tensile load by 1.04 to 1.06 times, but the ultimate load was 37.7 to 53.7% compared to the ductile cast iron or steel specimen without corrosion damage. It was found that the effect on the reinforcement of the corrosion damaged part was insignificant. Fourth, the composite sleeve using carbon fiber showed an ultimate load of 1.10(0.61T, 1,821.0 kgf) and 1.02(0.60T, 2,290.7 kgf) times higher than the ductile cast iron pipe(1,657.83 kgf) and steel pipe(2,236.8 kgf), respectively. When using a composite sleeve such as fiber, the corrosion damage part of large-diameter water pipes can be reinforced with same level as the original pipe, and the supply stability can be secured through accident prevention.

일반적인 불투과형 사방댐은 제체 대부분이 콘크리트로 구성되어 분리 및 해체가 어려워 조속한 보강이 난해하다는 단점이 있다. 이러한 단점을 보완하기 위한 투과형 강재 스크린 사방댐이 제작되어 사용 중에 있지만, 강재가 부식되는 등 여러 문제를 보이는 실정이다. 이에 따라, 선행 연구에서는 강재 스크린 구조물을 내부식성이 뛰어난 GFRP로 대체하여 성능 및 안전 성을 검증하였지만, 동수압만 고려되는 등 다양한 조건이 고려되지 않은 것으로 확인되었다. 그렇기에 본 연구에서는 선행 연구 에서 수행된 GFRP 스크린 구조물뿐만 아니라, CFRP도 고려하였으며, 보다 다양한 표면 유속 별 하중 조건 및 유목, 토석류 등 과 같은 다양한 조건에서의 성능 비교 및 안전성 평가를 수행하였다. 해석 결과, GFRP와 CFRP는 강재 대비 제체에 작용하는 응력이 29.79∼91.73%가량 감소된 성능을 보이며, 이 외에도 충분한 안전성과 경제성을 겸비함을 확인하였다. 결론적으로 GFRP 및 CFPR 스크린 구조물은 강재 투과형 사방댐을 대체하여 사용하기에 충분하다고 판단되지만, 이는 수치 해석을 통한 결과이 므로 향후 실제 실험이 진행될 필요가 있을 것으로 판단된다.

This study aimed to address the limitations of traditional plasma nitriding methods by implementing a short-term plasma oxy-nitriding treatment on the surface of AISI 420 martensitic stainless steel. This treatment involved the sequential formation of nitride and oxide layers, to enhance surface hardness and corrosion resistance, respectively. The process resulted in the formation of a 20 μm-thick nitride layer and a 3 μm-thick oxide layer on the steel surface. Initially, the hardness increased by 2.2 times after nitriding, followed by a subsequent decrease of approximately 31 % after oxidation. While the nitriding process reduced corrosion resistance, the subsequent oxidation process led to the formation of a passive oxide film, effectively resolving this issue. The pitting corrosion of the oxide passive film started at 82.6 mVssc, providing better corrosion resistance characteristics than the nitride layer. Consequently, the trade-off between surface hardness and corrosion resistance in plasma oxy-nitrided AISI 420 martensitic stainless steel is anticipated to be recognized as an innovative and comprehensive surface treatment process for biomedical components.

In order to broaden the range of application of light weight aluminum alloys, it is necessary to enhance the mechanical properties of the alloys and combine them with other materials, such as cast iron. In this study, the effects of adding small amounts of Cu and Zr to the Al-Si-Mg based alloy on tensile properties and corrosion characteristics were investigated, and the effect of the addition on the interfacial compounds layer with the cast iron was also analyzed. Although the tensile strength of the Al-Si-Mg alloy was not significantly affected by the additions of Cu and Zr, the corrosion resistance in 3.5 %NaCl solution was found to be somewhat lowered in this research. The influence of Cu and Zr addition on the type and thickness of the interfacial compounds layer formed during compound casting with cast iron was not significant, and the main interfacial compounds were identified to be Al5FeSi and Al8Fe2Si phases, as in the case of the Al-Si-Mg alloys.

Sealing treatment is a post-surface treatment of the plasma spray coating process to improve the corrosion resistance of the coating material. In this study, the effect of the sealing on the corrosion resistance and adhesive strength of the plasma spray-coated alumina coatings was analyzed. For sealing, an epoxy resin was applied to the surface of the coated specimen using a brush. The coated specimen was subjected to a salt spray test for up to 48 hours and microstructural analysis revealed that corrosion in the coating layer/base material interface was suppressed due to the resin sealing. Measurement of the adhesive strength of the specimens subjected to the salt spray test indicated that the adhesive strength of the sealed specimens remained higher than that of the unsealed specimens. In conclusion, the resin sealing treatment for the plasma spray-coated alumina coatings is an effective method for suppressing corrosion in the coating layer/base material interface and maintaining high adhesive strength.

In this study, corrosion fatigue crack propagation was investigated in pH buffer environment using the giga strength steel and its heat-affected zone, and the results were compared with theoretical model prediction. Also, the pure corrosion effect on fatigue crack propagation in a corrosive environment was compared with the modified Forman equation. As results, the average value of corrosion rate obtained as the ratio of the net corrosion-induced crack length to the total crack length under cyclic loading in the base metal and heat-affected zone under experimental loading conditions. These results exhibit a new theoretical method for corrosion fatigue crack propagation that predicts a purely corrosion effect on the behavior to be determined.

Novel Ni- and Fe-based alloys are developed to impart improved mechanical properties and corrosion resistance. The designed alloys are manufactured as a powder and deposited on a steel substrate using a high-velocity oxygen-fuel process. The coating layer demonstrates good corrosion resistance, and the thus-formed passive film is beneficial because of the Cr contained in the alloy system. Furthermore, during low-temperature heat treatment, factors that deteriorate the properties and which may arise during high-temperature heat treatment, are avoided. For the heattreated coating layers, the hardness increases by up to 32% and the corrosion resistance improves. The influence of the heat treatment is investigated through various methods and is considered to enhance the mechanical properties and corrosion resistance of the coating layer.

Corrosion is a natural, inevitable process, and is one of the world's most serious problems. Losses incurred due to corrosion are extremely expensive for society. Several technological strategies have been explored and implemented to address these losses. The use of inhibitors to prevent corrosion is a common and efficient method to reduce corrosion losses. This review covers Al and Al-composite corrosion inhibitors in chloride-containing solutions, because of their popularity in a broad array of industrial applications. A vast number of studies in the literature detail the common tendency of Al and Al-composites with reinforcements to deteriorate. Accordingly, it is worthwhile to employ inhibitors to protect them, as discussed in the present work. The emphasis is on selecting the smartest corrosion inhibitor and evaluating its performance. According to the study, the most commonly used corrosion inhibitors are 1,4-naphthoquinone (NQ), 1,5-naphthalene diol, 3-amino-1,2,4-triazole-5-thiol (ATAT), ammonium tetrathiotungstate, clotrimazole, amoxicillin, antimicrobial and antifungal drugs. Electrochemical impedance spectroscopy (EIS), potentiodynamic (PDP), and weight loss were among the most commonly used modern electrochemical technologies to test inhibitors’ efficacy under environmental conditions.