• Corrosion Science and Technology
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• 제3권3호
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• pp.118-126
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• 2004

The correlation between sensor output and corrosion rate of reinforcing steel was evaluated by laboratory electrochemical tests in saturated $Ca(OH)_2$ with 3.5 wt.% NaCl and confirmed in concrete environment. In this paper, two types of electrochemical probes were developed: galvanic cells containing of steel/copper and steel/stainless steel couples. Potentiodynamic test, weight loss measurement, monitoring of open-circuit potential, linear polarization resistance (LPR) measurement and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior of steel bar embedded in concrete. Also, galvanic current measurements were conducted to obtain the charge of sensor embedded in concrete. In this study, steel/copper and steel/stainless steel sensors showed a good correlation in simulated concrete solution between sensor output and corrosion rate of steel bar. However, there was no linear relationship between steel/stainless steel sensor output and corrosion rate of steel bar in concrete environment due to the low galvanic current output. Thus, steel/copper sensor is a reliable corrosion monitoring sensor system which can detect corrosion rate of reinforcing steel in concrete structures.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.526-529
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• 2008

The effect of air impurities on PEMFC performances were studied using electrochemical analysis, such as OCV monitoring, polarization, constant current operation, and electrochemical impedance spectroscopy. The nitrogen dioxide in air lowered the operation voltage at 1 A/$cm^2$ by 160 mV (10 ppm) and 227 mV (100 ppm), while the carbon monoxide effect was relatively not significant (30 mV at 100 ppm). For both nitrogen dioxide and carbon monoxide, the performances were largely recovered when pure air was provided again. Further study for additional air impurities and simulated air are under progress to provide fundamental data for the design of fuel cell vehicles.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.57-58
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• 2022

Reinforced concrete (RC) structures play a significant role in the construction industries. An embeddable solid-state reference electrode (ESSRE) was used to evaluate the corrosion status of steel rebar in the concrete of various cover thicknesses that exposed to the maritime environment (3.5 % NaCl) in this study. From the open circuit potential measurement (OCP), the passive state, the corrosion uncertainty, and the 90% probability of corrosion state of the steel rebars in the concrete were monitored by ESSRE. From the electrochemical impedance spectroscopy (EIS) method, severe corrosion was observed at the exposure period of 1510, 1847, 2350, and 3020 h for C10, C15, C20, and C30 concrete, respectively. The results confirm that the ESSRE can be useful to identify the corrosion occurrence and severe corrosion of steel rebar embedded in different cover depth concrete structures.

• 한국구조물진단유지관리공학회 논문집
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• 제26권6호
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• pp.82-92
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• 2022

본 연구의 목적은 3전극방식으로 전기화학적 임피던스분광법(EIS)를 활용한 콘크리트 속 철근의 분극저항을 측정할 때 전기화학 셀저항에 따른 인가전압의 변화를 실험적으로 확인하고, 안정적인 측정값을 획득을 위한 실험조건을 찾는 것이다. 본 연구에서는 셀저항을 구성하는 요소 중 콘크리트 건조상태, 전극의 커플링상태(접촉저항) 및 상대전극의 면적을 주요변수 설정하였다. 본 연구에서는 지름 200mm인 정사각형 콘크리트 실험체 중심에 D22 철근이 부분적으로 매입된 실험체를 준비하여, 주요변수의 조합으로 구성된 다양한 실험조건에서 EIS을 수행하였으며 이때 포텐쇼스탯에서 인가된 전압을 측정하였다. 본 연구의 실험결과를 통하여, 3전극 방식으로 콘크리트 속 철근의 부식속도를 측정할 경우, 측정장치의 추종전압보다 측정 시 요구되는 인가전압이 충분히 큰 경우 셀저항의 변화는 EIS 측정에 큰 영향을 주지 않는 것을 확인하였다. 참조전극과 기준전극을 콘크리트 표면에 부착된 상태에서 EIS에서 콘크리트의 건조상태 및 상대전극의 면적에 대한 영향에 비하여 전극과 표면의 접촉저항의 영향이 지배적인 것을 확인하였다. 본 연구의 결과는 해양환경에 노출된 콘크리트와 같이 침지 및 건조 반족 조건에 노출된 콘크리트에서 3전극방식의 EIS 측정으로 철근 부식속도 및 상태평가를 위한 센서 개발에 기본 데이터로 활용될 수 있다.

• 한국해양공학회지
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• 제27권3호
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• pp.8-14
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• 2013

Although there are various factors that threaten the security of ships, one of the most harmful is corrosion. It is not easy to find corroding areas and the status of corrosion, even though corrosion causes serious problems such as submergence and marine pollution as a result of leaking oil and polluted water. To monitor the corrosion of ships, non-destructive inspection, weight loss coupons, electrical resistance, linear polarization resistance, zero resistance ammeter, and electrochemical impedance spectroscopy have been developed. However, these methods require much time to detect corrosion, and most are not appropriate for real time monitoring. Coating, sacrificial anode, and impressed current cathodic protection (ICCP) methods have been developed to control corrosion. The ICCP and sacrificial anode methods are the most popular ways to prevent ship corrosion. However, ICCP is only appropriate for the outside of a ship and cannot be used for complex structures such as ballast tanks because these are composed of many separate chambers. Sacrificial anodes have to be replaced periodically. This paper proposes an integrated corrosion monitoring and control system (ICMCS) that can detect corrosion in real time and is appropriate for complex structures such as ballast tanks. Because the system uses titanium for an anode, exhausted anodes do not need to be replaced.

• 한국자동차공학회논문집
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• 제22권7호
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• pp.76-83
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• 2014

During PEMFC(Proton Exchange Membrane Fuel Cell) operation monitoring and diagnosis are important issues for reliability and durability. Stack defect can be followed by a critical cell voltage drop in the stack. One method for monitoring the cell voltage is CVM(Cell Voltage Monitoring), where all cells in the stack are electrically connected to a voltage measuring system and monitored these voltages. The other methods are based on the EIS(Electrochemical Impedance Spectroscopy) and on nonlinear frequency response. In this paper, intermodulation(IM) method for diagnosis PEMFC stack is introduced. To detect one or more critical PEMFC cell voltage PEMFC stack is excited by two or more test sinusoid current, and the frequency response of the stack voltage is analyzed. If one or more critical cell voltage exists, higher harmonics on the voltage frequency spectrum will appear. For the proposed IM method, stack simulation and experiments are conducted.

• 전기화학회지
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• 제18권4호
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• pp.137-142
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• 2015

$Mn_{1+X}Co_{2-X}O_4$ solid solutions with various Mn/Co ratios were synthesized by a combustion method, and used as cathode catalysts for lithium/air secondary battery. Their electrochemical and physicochemical properties were investigated. The morphology was examined by transmission electron microscopy (TEM), and the crystallinity was confirmed by X-ray diffraction (XRD) analyses. For the measurement of electrochemical properties, charge and discharge measurements were carried out at a constant current density of $0.2mA/cm^2$, monitoring the voltage change. Electrochemical impedance spectroscopy (EIS) analyses were also employed to examine the change in charge transfer resistance during charge-discharge process. $Mn_{1+X}Co_{2-X}O_4$ solid solutions showed enhanced cycleability as a cathode of Li/air secondary battery, and the performance was found to be strongly dependent on Mn/Co ratio. Among synthesized catalysts, $Mn_{1.5}Co_{1.5}O_4$ exhibited the best performance and cycleability, due to high charge transfer rate.

• Molecules and Cells
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• 제39권11호
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• pp.807-813
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• 2016

Escherichia coli are important indicator organisms, used routinely for the monitoring of water and food safety. For quick, sensitive and real-time detection of E. coli we developed a 2'F modified RNA aptamer Ec3, by Cell-SELEX. The 31 nucleotide truncated Ec3 demonstrated improved binding and low nano-molar affinity to E. coli. The aptamer developed by us out-performs the commercial antibody and aptamer used for E. coli detection. Ec3(31) aptamer based E. coli detection was done using three different detection formats and the assay sensitivities were determined. Conventional Ec3(31)-biotin-streptavidin magnetic separation could detect E. coli with a limit of detection of $1.3{\times}10^6CFU/ml$. Although, optical analytic technique, biolayer interferometry, did not improve the sensitivity of detection for whole cells, a very significant improvement in the detection was seen with the E. coli cell lysate ($5{\times}10^4CFU/ml$). Finally we developed Electrochemical Impedance Spectroscopy (EIS) gap capacitance biosensor that has detection limits of $2{\times}10^4CFU/mL$ of E. coli cells, without any labeling and signal amplification techniques. We believe that our developed method can step towards more complex and real sample application.