• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.6
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• pp.569-576
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• 2012

In general, aluminum alloys forms the passive film($Al_2O_3$, $Al_2O_3{\cdot}3H_2O$) in neutral solution. However, the passive film created on the surface will be destroyed by chloride ions contained in sea water so the corrosion will occur. In this study, in order to solve the problem of corrosion under a seawater environment, potentiostatic protection techniques were applied to Al-4.5%Mg-0.6%Mn aluminum alloy in seawater. At polarization experiments, active state were observed at anodic polarization and concentration polarization by reduction of dissolves oxygen and activation polarization were found at anodic polarization. As a results of potentiostatic experiment, calcareous deposit were created much more as applying time increase from the turning point of the concentration polarization and activation polarization and crevice corrosion was partially observed between calcareous deposit and surface of base metal. Overall potentiostatic anodic polarization experiment was difficult to apply potentiostatic corrosion protection technology by occurrence of active state, whereas potentiostatic cathodic polarization experiment examined optimum corrosion protection condition of -1.1 V~-0.75 V within the range of concentration polarization considered various applying time.

• Journal of the Korean institute of surface engineering
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• v.39 no.1
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• pp.18-24
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• 2006

Although stainless steels have the excellent corrosion resistance by passive film, they are susceptible to pitting corrosion in the environment containing halogen elements such as chloride ions. The resistance to pitting corrosion can be evaluated by measuring the critical pitting temperature (CPT). CPT values can be obtained using immersion, potentiodynamic and potentiostatic polarization test methods. Results on duplex 2205 stainless steels showed that CPT values were measured as $50^{\circ}C,\;55^{\circ}C\;and\;61^{\circ}C$, respectively for immersion, potentiodynamic and potentiostatic polarization test methods, depending upon the different test methods, even though the difference between CPT values are not much.

• Corrosion Science and Technology
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• v.10 no.4
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• pp.125-130
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• 2011

This study was performed to improve the corrosion resistance and the stability of passive film on copper tube by potentiostatic polarization method in synthetic tap water. Formation of passive film was carried out by anodic potentiostatic polarization at various passivation potentials and passivation times in 0.1 M NaOH solution. Stability of passive film and corrosion resistance was evaluated by self-activation time, ${\tau}_0$ from passive state to active state on open-circuit state in 0.1 M NaOH solution. Addition of polyphosphate in NaOH solution prolonged the self-activation time and improved the corrosion resistance, and the addition of 5 ppm polyphosphate was most effective. It was also observed that better corrosion resistance was obtained by potentiostatic polarization at 1.0 V (vs. SCE) than at any other passivation potentials. Passivated copper tube showed perfect corrosion resistance for the immersion test in synthetic tap water showing that the anodic potentiostatic polarization treatment in 0.1 M NaOH with 5 ppm polyphosphate solution would be effective in improving the corrosion resistance and preventing the blue water problem.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.3
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• pp.247-260
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• 2010

The developement of a HLW disposal canister is under way in KAERI using Cold Spray Coating technique. To estimate corrosion behavior of a cold sprayed copper, a creivice corrosion test was conducted at Southwest Research Institute(SWRI) in the United State. For the measurement of repassivation potential needed for crevice corrosion, three methods such as (1) ASTM G61-86 : Cyclic Potentiodynamic Polarization Measurements, (2) Potentiodynamic Polarization plus intermediate Potentiostatic Hold method, and (3) ASTM G192-08 (THE method) : Potentiodynamic- Galvanostatic-Potentiostatic Method, were introduced in this report. In the crevice corrosion test, the occurrence of corrosion at crevice area was optically determined and the repassivation potentials were checked for three kind of copper specimens in a simulated KURT underground water, using a crevice former dictated in ASTM G61-86. The applied electrochemical test techniques were cyclic polarization, potentiostatic polarization, and electrochemical impedance spectroscopy. As a result of crevice corrosion tests, every copper specimens including cold sprayed one did not show any corrosion figure on crevice areas. And the open-cell voltage, at which corrosion reaction initiates, was influenced by the purity of copper, but not their manufacturing method in this experiment. Therefore, it was convinced that there is no crevice corrosion for the cold sprayed copper in KURT underground environment.

• Corrosion Science and Technology
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• v.5 no.5
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• pp.160-167
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• 2006

S-Acetyl Isothiourea Acetate (S-AITA) was synthesized in the laboratory and this influence on the inhibition of corrosion of mild steel in 1.11 N hydrochloric and 1.12 N sulphuric acids was investigated by weight loss and potentiostatic polarization techniques at 303K, 353K and 403K. These results were confirmed by the impedance technique. The inhibition efficiency increased with increase in concentration of inhibitor and decreased with rise in temperature from 303K to 403K. The maximum inhibition efficiency of S-AITA was found to be 99.95% (0.5% of S-AITA) at 303K in sulphuric acid. The adsorption of this compound on the mild steel surface from the acids has been found to obey Temkin's adsorption isotherm. The potentiostatic polarization results revealed that S-AITA was a mixed type inhibitor. Some thermodynamic parameters i.e., activation energy (Ea), free energy of adsorption (${\Delta}G_{ads}$), enthalpy of adsorption (${\Delta}H$) and entropy of adsorption (${\Delta}S$) were also calculated from weight loss data.

• Journal of Technologic Dentistry
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• v.38 no.2
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• pp.79-84
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• 2016

Purpose: The aim of this study was to make nanomesh on the surface of titanium by potentiostatic technique which was done at the suitable potential level. Methods: In order to find the suitable potential level, use a $25^{\circ}C$ NaCl, NaOH and NH4F solution of 1 M and 5 M as supporting electrolyte, working electrode(positive potential) was contact to the titanium specimen and counter electrode(negative potential) was contact to the Pt substrate. At the transpassive potential which was observed by potentiostatic technique, potentiostatic technique was done for 2hours. Results: As a result, 1 M NaOH solution was suitable as a supporting electrolyte, potentiostatic technique used a $25^{\circ}C$ NaOH solution of 1 M for 2hours, nanomesh was formed. Conclusion: The potentiostatic technique was used $25^{\circ}C$ NaOH solution of 1 M and 5 M as supporting electrolyte for 2hours. Nanomesh was built more uniform and fine in 1 M NaOH solution than 5 M NaOH solution.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.230-237
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• 2017

In this study, electrochemical methods were used to determine the optimum protection potential of S355ML steel for the cathodic protection of offshore wind-turbine-tower substructures. The results of potentiodynamic polarization experiments indicated that the anodic polarization curve did not represent a passivation behavior, while under the cathodic polarization concentration, polarization was observed due to the reduction of dissolved oxygen, followed by activation polarization by hydrogen evolution as the potential shifted towards the active direction. The concentration polarization region was found to be located between approximately -0.72 V and -1.0 V, and this potential range is considered to be the potential range for cathodic protection using the impressed current cathodic protection method. The results of the potentiostatic experiments at various potentials revealed that varying current density tended to become stable with time. Surface characterization after the potentiostatic experiment for 1200 s, by using a scanning electron microscope and a 3D analysis microscope confirmed that corrosion damage occurred as a result of anodic dissolution under an anodic polarization potential range of 0 to -0.50 V, which corresponds to anodic polarization. Under potentials corresponding to cathodic polarization, however, a relatively intact surface was observed with the formation of calcareous deposits. As a result, the potential range between -0.8 V and -1.0 V, which corresponds to the concentration polarization region, was determined to be the optimum potential region for impressed current cathodic protection of S355ML steel.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.152-152
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.999-1002
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• 2002

In this research, the mechanism of micro-ECM was investigated with potentiodynamic method and the optimal condition for micro-ECM was selected by voltage-current-time curve with potentiostatic method. From the experimental result. it was confirmed that anodic voltage curve could be used very effectively for determining the optimal condition of micro-ECM, and the micro part which has extremely fine surface could be fabricated by use of micro-ECM with point electrode method.

• Journal of the Korean Electrochemical Society
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• v.7 no.4
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• pp.179-182
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• 2004

The aim of this study is to investigate the initiation and propagation of crevice corrosion for ferritic stainless steel in artificial crevice based on micro capillary tube method. The 430 stainless steel in artificial crevice is potentiostatically polarized in different sodium chloride solutions. Potentiodynamic and potentiostatic polarization data were measured in situ. The potentials in the crevice were measured by depth profile using the 0.04 mm diameter micro capillary tube inserted in the crevice. The potentials in the crevice ranged from -220 mV to -360 mV vs SCE from opening to bottom of crevice, which are lower than the external surface potential, -200 mV vs SCE. Such a potential drop induced the change of the metal surface state from passive to active. The surface of metal is located in passive state in -200 mV but the inner surface keeps active state below -220 mV, Thus these results show that the It drop mechanism in the crevice was more objective for evaluation and the method was easier to reproduce. Therefore the potential drop is one of the reasons for crevice corrosion by measuring the potentials in narrow crevice with a new micro measuring system.