• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.311-320
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• 1998

The cryogenic fracture behaviors of austenitic stainless steel HN2 developed for nuclear fusion reactor were evaluated quantitatively by using the small punch(SP) test. The electrochemical polarization test was applied to study thermal aging degradation of HN2 steel. The X-ray diffraction(XRD) analysis was conducted to detect carbides and nitrides precipitated on the grain boundary of the heat treated HN2 steel. The mechanical properties of the HN2 steel significantly decreased with increasing time and temperature of heat treatment or with decreasing testing temperature. The integrated charge(Q) obtained from electrochemical polarization test showed a good correlation with the SP energy(ESP) obtained by means of SP tests. From the results observed in the x-ray diffraction and anodic polarization curve, it was known that the material the grain boundary. Combining SP test and electrochemical polarization test, it could be useful tools to non-destructively evaluate the cryogenic fracture behaviors and the aging degradation for cryogenic structural material.

• 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.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.5
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• pp.702-711
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• 1998

The characteristics of corrosion resistance for the surface of medium high carbon steels and low alloy steels utilizing as manufacturing the machinery structures and machining tools and treating by plasma/ion nitriding process have been studied in terms of electrochemical polarization behav-iors including corrosion potential(Ecorr) anodic polarization trends and polarization resistance(Rp) The seven base materials showed a clear passivation behavior for the polarization tests in the ASTM standard solution 1N ${H_2){SO_4}$ Although the treated surface by plasma nitriding for the seven test materials showed a significant increase in hardness the treatment gave a detri-mental effect in corrosion resistance. The various characteristics including corrosion potential polarization curves microstructures corrosion current polarization resistance among non-treat-ed nitriding and/or soft-nitriding treated specimens have been investigated and some of the mechanisms discussed.

• Journal of Fisheries and Marine Sciences Education
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• v.18 no.1
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• pp.58-64
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• 2006

In order to examine the effect of humidity on hydrogen embrittlement of STS 444 weld zone for boiler with dry and wet welding conditions, this paper was carried out the accelerated hydrogen osmosis test and the electrochemical Tafel polarization test. In 0.5M $H_2SO_4$ + 0.01M $As_20_3$ solution, this test is added to load of $1400kg/cm^2$ together with hydrogen osmosis by current of $50 {mA/cm^2}$ for 60 min.. The electrochemical Tafel polarization test was carried out in 0.5M $H_2SO_4$ + 0.01M $As_20_3$ solution. Therefore, the effect of humidity on hydrogen embrittlement of STS 444 was considered. The main results are as following: On the basis of hydrogen embrittlement mechanism, that is, integrated electrochemical polarization characteristics with the established mechanism of hydrogen embrittlement, the reduction rate of corrosion current density of weld zone in the wet weld condition is larger than in the dry condition. We can nondestructively predict the degree of hydrogen embrittlement of STS 444 weld zone for boiler through the reduction rate of electrochemical corrosion current density.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.4
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• pp.417-425
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• 2016

Desalination is a key technology to overcome water shortage problem in a near future. High energy consumption is an Achilles' heel in desalination technology. Osmotically driven membrane processes like forward osmosis(FO) was introduced to address this energy issue. Characterizing membrane properties such as water permeability(A), salt permeability(B), and the resistance to salt diffusion within the support layer($K_{ICP}$) are very important to predict the performance of scaled-up FO processes. Currently, most of researches reported that the water permeability of FO membrane was measured by reverse osmosis(RO) type test. Permeating direction of RO and FO are different and RO test needs hydraulic pressure so that several problems can be occurred(i.e. membrane deformation, compaction and effect of concentration polarization). This study focuses on measuring water permeability of FO membrane by FO type test results in various experimental conditions. A statistical approach was developed to evaluate the three FO membrane properties(A, B, and $K_{ICP}$) and it predicted test result by the internal and external concentration polarization model.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.534-537
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• 2005

Polarization of the radar wave refers to the ellipticity angle and orientation angle of the polarization ellipse. An evaluation of the polarization response can help understand the scattering mechanisms involved for a particular area of interest or provide information for image classification and algorithm section. C- and L-band polarization responses measured at urban area show the results that the polarization behavior for dihedral comer reflector or short, thin cylinder reflector appears at located in city streets or buildings site which are lined up and the polarization behavior for a large conducting sphere appears at parts of test site particularly river, flat, and vegetated areas. Also, the co- and cross-polarized response graphs and polarimetric parameters are discussed.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.143-148
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• 2001

This research was undertaken to clarify effects of thermal aging on electrochemical and mechanical properties of superaustenitic stainless steel. The steel was artificially aged at $300{\sim}650^{\circ}C$ for $240{\sim}10,000hrs$. and investigated at $-196{\sim}650^{\circ}C$ using small punch(SP) test. Also, the change in electrochemical properties caused by effects of thermal aging was investigated using electrochemical anodic polarization test in a KOH electrolyte. Carbides and ${\eta}-phase(Fe_2Mo)$ precipitated in the grain bounderies seem to deteriorate the mechanical properties by decreasing cohesive strength in the grain bounderies and promote the current density observed in electrochemical polarization curves. The electrochemical and mechanical properties of superaustenitic stainless steel was drastically decreased in the specimen aged at $650^{\circ}C$.

• 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.

• Journal of Technologic Dentistry
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• v.26 no.1
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• pp.41-48
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• 2004

Ti-20%Zr(-5%Cr) alloys not containing harmful Al and V were newly designed in order to reveal their possibility for dental casting and melted in an arc melting and casting furnace under Ar atmosphere. The corrosion resistance was studied by anodic polarization test. From the observation of anodic polarization behavior, it was found that the corrosion resistance was markedly increased by the addition of Cr. The corrosion resistance of Ti-20%Zr-5%Cr alloy was superior to that in Ti-6%Al-4%V alloy but almost similar to that in CP Ti using in market place today.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1241-1249
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• 2002

The extent of materials deterioration can be evaluated accurately by mechanical test such as impact test or creep test. But it is almost impossible to extract a large test specimen from in-service components. Thus material degradation evaluation by non-destructive method is earnestly required. In this paper, the material degradation for virgin and several aged materials of a Cr-Mo-V steel, which is an candidated as structural material of the turbine casing components for electric power plant, is nondestructively evaluated by reactivation polarization testing method. And, the results obtained from the test are compared with those in small punch(SP) tests recommended as a semi-nondestructive testing method using miniaturized specimen. In contrast to the aged materials up to 1,000hrs which exhibit the degradation behaviors with increased ${\Delta}[DBTT]_{SP}$, the improvement of mechanical property can be observed on the 2,000hrs and 3,000hrs aged materials. This is because of the softening of material due to the carbide precipitation, the increase of ferritic structures and the recovery of dislocation microstructure by long-time heat treatment. The reactivation rates($I_R/I_{Crit},\;Q_R/Q_{Crit}$) calculated by reactivation current densityt ($I_R$) and charge($Q_R$) in the polarization curves exhibit a good correlation with ${\Delta}[DBTT]_{SP}$ behaviors.