• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2378-2383
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• 2007

Direct Numerical Simulation was carried out to predict mass transfer in turbulent flow around a rotating stepped cylinder. This investigation is a follow-up study of Nesic et al. [Corrosion, Vol. 56, No. 10, pp. 1005 - 1014] The original motivation of this work stemmed from the efforts to design a simple device which can generate flows of high turbulence intensity at low cost for corrosion researchers. Two cases were considered; Sc=1 and 10 both at Re=335. Here, Sc and Re stand for Schmidt number and Reynolds number, respectively, based on the step height and the surface speed of the cylinder upstream the step. Main focus was placed on the correlation between turbulent fluctuation and concentration field. The spatio-temporal evolution of concentration field is discussed. The numerical results are qualitatively compared with those of the experiment conducted with the same flow configuration.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.1045-1050
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• 2001

This study was performed to evaluate reinforced concrete durability in chloride attack environment under sustained load by the corrosion of reinforcing bars and the permeation of chloride ion. Generally, it is regarded that permeability of chloride ion is determined by the properties of concrete, but the effects of load which make alternation of concrete inner structure such as crack and so on should not neglected. In this study, it is shown that the relation between bending load on RC beam, deflection and crack of specimen, permeation of chloride ion, rating of re-bar corrosion, and the relation between compression load and permeation of chloride ion. Therefore the effects of load on permeation of chloride ion and re-bar corrosion are evaluated.

• 공업화학
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• 제9권5호
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• pp.674-679
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• 1998

액체금속로 증기발생기 전열관 재질로 사용이 예상되는 ferrite steel 시편을 사용해서 소듐분위기에서 미량의 물 누출 실험을 수행하였다. 누출경로는 소듐-물 반응생성물 및 부식생성물에 의한 self-plugging 현상과 열적인 transient 및 전열관의 vibration에 의한 re-opening 메카니즘으로 설명이 가능하였다. 실험결과, 600 Psig의 injection 압력으로 5 g $H_2O$를 소듐분위기 속의 시편으로 누출시킨 경우, 누출초기와 약 70분 경과 후에 약간의 누출 흔적이 보였으나, self-plugging되었던 누출경로는 129분이 경과되자 완전 re-opening된 것으로 확인되었다. 누출시편의 re-opening shape은 2중으로 되어 있었으며, 소듐부위에서 시편 표면에 나타난 re-opening size 약 2 mm의 직경을 나타내었다.

• Corrosion Science and Technology
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• 제20권1호
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• pp.37-43
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• 2021

Additively manufactured (AM) Ti-6Al-4V alloys exhibit a dominant acicular martensite phase (α'), which is characterized by an unstable energy state and highly localized corrosion susceptibility. Electrochemical critical localized corrosion temperature (E-CLCT, ISO 22910: 2020) and electrochemical critical localized corrosion potential (E-CLCP, ISO AWI 4631: 2021) were measured to analyze the localized corrosion resistance of the AM Ti-6Al-4V alloy. Although E-CLCP was measured under mild corrosive conditions such as human body, the validity of evaluating localized corrosion resistance of AM titanium alloys was demonstrated by comparison with E-CLCT. However, the mechanisms of resistance to localized corrosion on the as-received and heat-treated AM Ti-6Al-4V alloys under E-CLCT and E-CLCP differ at various temperatures because of differences in properties under localized corrosion and repassivation. The E-CLCT is mainly measured for initiation of localized corrosion on the AM titanium alloys based on temperature, whereas the E-CLCP yields repassivation potential of re-generated passive films of AM titanium alloys after breaking down.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.279-284
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• 2002

The expected life of the hot stove equipments for #2 blast furnaces in Gwangyang Steel Works is about 40 years. However, the stress corrosion cracking(SCC) are founded in heat affected zone only 10 years operation. In this paper, the mechanism of SCC are investigated and the preventive measures are recommended.

• Corrosion Science and Technology
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• 제21권6호
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• pp.454-465
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• 2022

The objective of this study was to determine effects of temperatures and pH of sodium chloride solution with MgCl₂ ions on corrosion resistance of duplex stainless-steel X2CrNiMoN22-5-3 (DSS) and Ti 6Al 2Nb1Ta1Mo (Ti). Effects of sodium chloride concentration on corrosion resistance were also studied. Corrosion behavior and pitting morphology of duplex stainless steel (DSS) and Ti alloys were evaluated through potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). It was found that a decrease in pH significantly reduced the corrosion resistance of both alloys. Changes in chloride concentration and temperature had more substantial impact on corrosion behavior of DSS than on Ti alloys. Pitting corrosion was formed on DSS samples under all conditions, whereas crevice corrosion was developed on Ti samples with the presence of magnesium chloride at 90 ℃. In conclusion, magnesium chloride ions in an exceedingly strong acidity solution appear to interact with re-passivation process at the surface of these alloys and influence the resulting surface topography.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.129-133
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• 1995

The purpose of this study is to evaluate the flexural bond performance in beam using 3-types anti-corrosion coatings. For the test. we used $15\times\times20\times110cm$ R.C beams, in which the epoxy, the red lead, and the cementitious anti-corrosion coating re-bars used. The results of test using these 3-type anti-corrosion coatings are shown that the flexural bond performance of cementitious anti-corrosion coating rebar in R.C beam is superior to other anti-corrosion coatings rebars.

• 한국주조공학회지
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• 제35권3호
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• pp.45-52
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• 2015

The effect of different C and Cr/Mo contents, which were varied within the range allowed in the relevant specification, on the mechanical and corrosion properties of A487 alloy cast steel were examined. The increase in strength level with increasing C content and the decrease in strength along with the increase in tensile elongation with decreasing Cr/Mo contents were observed in A487 alloys with different C and Cr/Mo contents. At room temperature, the decrease in Cr/Mo content was beneficial in improving the impact properties of A487 alloy, with no notable difference in absorbed energy with varying C content. The impact properties of A487 alloy at $-60^{\circ}C$, on the other hand, greatly improved with the increase in C and the decrease in Cr/Mo contents. The corrosion behavior of A487 alloys in 3.5% NaCl solution did not show any meaningful change with different C and Cr/Mo contents.

• 대한금속재료학회지
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• 제50권5호
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• pp.353-360
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• 2012

The corrosion product of archaeological iron objects is supposed to be removed because it causes re-corrosion. So far it is removed by scapel and sand blaster but they depend on the skill and experience of a conservator and the glass-dust of the sand blaster is harmful to humans. Therefore this study applies a laser cleaning system which is used in various industrial cleaning processes, to remove corrosion product from archaeological iron objects. In addition, this work studies the alternation of corrosion product after laser irradiation, which evaluates the reliability of the laser cleaning system. Optical microscopy, SEM-EDS, XRD, Raman have been used to observe and analyse the surface of the objects. The results show the capacity of laser cleaning some corrosion product, but blackening appears with increasing pulses and laser energy, and some corrosion products, goethite and hematite, are partially altered to magnetite. These problems, blackening and alternation of corrosion product, should be solved by further studies which find the optimal laser irradiation condition and use a wetting agent.

• 한국재료학회지
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• 제28권12호
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• pp.738-747
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• 2018

For the aerospace structural application of high-strength 2xxx series aluminum alloys, stress corrosion cracking(SCC) behavior in aggressive environments needs to be well understood. In this study, the SCC sensitivities of 2024-T62, 2124-T851 and 2050-T84 alloys in a 3.5 % NaCl solution are measured using a constant load testing method without polarization and a slow strain rate test(SSRT) method at a strain rate of 10-6 /sec under a cathodic applied potential. When the specimens are exposed to a 3.5 % NaCl solution under a constant load for 10 days, the decrease in tensile ductility is negligible for 2124-T851 and 2050-T84 specimens, proving that T8 heat treatment is beneficial in improving the SCC resistance of 2xxx series aluminum alloys. The specimens are also susceptible to SCC in a hydrogen-generating environment at a slow strain rate of $10^{-6}/sec$ in a 3.5 % NaCl solution under a cathodic applied potential. Regardless of the test method, low impurity 2124-T851 and high Cu/Mg ratio 2050-T84 alloys are found to have relatively lower SCC sensitivity than 2024-T62. The SCC behavior of 2xxx series aluminum alloys in the 3.5 % NaCl solution is discussed based on fractographic and micrographic observations.