• 한국주조공학회지
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• 제36권4호
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• pp.117-125
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• 2016

The effects of the Zn content on the microstructure and corrosion behavior in 1M NaCl solution were investigated in Mg-(0~6)%Zn casting alloys. The MgZn phase was scarcely observed in the Mg-1%Zn alloy, while the Mg-(2~6)%Zn alloy consisted of ${\alpha}$-(Mg) and MgZn phases. With an increase in the Zn content, the amount of the MgZn phase was gradually increased. Immersion and electrochemical corrosion tests indicated that the Mg-1%Zn alloy had the lowest corrosion rate among the alloys, and a further increase in the Zn content resulted in the deterioration of the corrosion resistance. Microstructural examinations of the corroded surfaces and EIS analyses of surface corrosion films revealed that the best corrosion resistance at 1%Zn was associated with the absence of MgZn phase particles in the microstructure and the contribution of Zn element to the formation of a protective film on the surface. A micro-galvanic effect by the MgZn particles led to the increased rate of corrosion at a higher Zn content.

• 동력기계공학회지
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• 제18권6호
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• pp.29-33
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• 2014

The electrochemical characteristics of Al-Si casting alloys (Al-10%Si, Al-9%Si, Al-7%Si) in 3.5% NaCl solution at room temperature was studied using potentiodynamic techniques. The electrochemical values of corrosion potential($E_c$), corrosion current density($I_c$) and corrosion rate(mpy) were examined. The Al-Si alloys had several compounds such as $Mg_2Si$, ${\pi}$-$Al_8Si_6Mg_2Fe$ and $Al_2CuMg$ which could affect corrosion resistance significantly. The potentiodynamic polarization curve exhibited typical active behavior in anodic polarization curve. The major corrosion mechansim for the Al-Si alloys were pitting and grain boundary corrosion. As increasing Si and Cu contents, their corrosion resistance was decreased.

• 한국도로학회논문집
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• 제11권3호
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• pp.51-60
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• 2009

본 연구에서는 고강도 고내구성 시멘트콘크리트 포장을 위하여 도출된 배합 콘크리트의 굳지않은 콘크리트 특성, 강도발현 특성, 염소이온의 투수특성 및 동결-융해에 대한 저항성 등의 역학적 내구적 특성을 분석하였다. 제시된 배합의 목표스럼프와 공기량은 적절한 혼화제의 사용으로 확보가 가능하나, 혼화제의 적정사용량은 충분한 현장배합실험을 통하여 구하여야 할 것이다. 단위시멘트량을 증가한 경우 일반적으로 강도가 증가하였으며 특히 재령 28일 이후의 강도가 지속적으로 증가하는 양상을 나타내었다. 휨강도는 그 특성상 단위시멘트량을 증가하더라도 뚜렷한 효과는 나타나지 않았다. 염소이온 침투저항성도 단위시멘트량보다는 재령에 따른 영향을 더 크게 받는 것으로 나타났다. 공기량에 가장 많은 영향을 받는 동결-융해 저항성은 각 실험변수에 대한 시험체를 공기량이 3% 이하 및 이상인 경우에 대하여 그리고 동결시 수돗물을 사용한 경우와 현장의 열악한 환경을 모사하기 위하여 4%의 NaCl 용액을 사용한 경우로 구분하여 실시하였다. 공기량에 상관없이 수돗물을 사용한 경우에는 동결-융해반복회수가 300회까지 상대동탄성계수나 표면의 손상이 거의 발생하지 않았다. 4% NaCl 용액을 사용한 경우에는 단위시멘트량이 현재의 한국도로공사의 표준배합인 경우 손상이 발생하였으며, 단위시멘트량이 동결-융해 저항성에 미치는 영향이 큰 것으로 나타났다. 따라서, 동결-융해에 대한 저항성을 충분히 확보하는 고내구성의 시멘트콘크리트 포장을 위해서는 단위시멘트량을 현재의 수준보다 증가시키는 것이 유리한 것으로 판단되며, 실험결과로부터 이러한 요구성능을 발휘하기 위해서는 단위시멘트량을 400kg/$m^3$ 이상으로 할 것을 권장한다.

• 대한소아치과학회지
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• 제27권2호
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• pp.370-378
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• 2000

심미성 수복재로서 임상에서 널리 사용되는 복합레진은 구강내에서 장기간 유지되도록 하기 위하여 그 물성을 향상시킬 필요가 있다. 복합레진의 단점 중 하나로 낮은 마모저항성을 들수 있으며, 이와 관련된 하나의 인자로 수복물의 표면하 분해(subsurface degradation)가 고려되고 있다. 본 연구에서는 알카리성 용액(0.1N NaOH)에 현재 임상에서 많이 이용되는 Clearfil APX (CL, Kuraray). Heliomolar (H,Vivadent), Surefil (S, Dentsply), Tetric Ceram (TC, Vivadent), TPH (Dentsply), Z100 (3M)의 6종의 복합레진을 보관하였을 때 각 제품의 분해저항성을 평가하고자 하였다. 각 제품당 3개의 시편을 제작하여 무게측정을 한 후 0.1N NaOH용액에 저장하여 $60^{\circ}C$에서 보관하였다. 2주후 제거하여 HCl로 중화, 세척 후 $60^{\circ}C$에서 건조하였다. 무게손실, 분해층 깊이, Si 농도등을 기준으로 분해저항성을 평가하여 다음과 같은 결과를 얻었다. 1. 각 제품의 무게손실량은 $0.45\sim3.64%$ 까지 다양하며 Z100, TC, H, S, CL, TPH 순으로 많았다. 2. 각 제품의 표면하 분해층 깊이는 제품마다 다양하여, $10.85\sim73.38{\mu}m$의 범위였고, H, Z100, S, TC, TPH, CL 순으로 깊었다. 3. 각 제품으로부터 용출된 Si 양은 Z100군 2060ppm으로 가장 많고, H, TPH, CL, TC, S순으로 많았다. 4. 무게손실량과 표면하 분해층 깊이사이에 높은 상관관계를 보였다. (r=0.81, p,0.05) 5. 주사전자현미경하 관찰시 NaOH 용액에 보관한 후 레진기질과 필러사이의 결합의 파괴를 관찰할 수 있었다.

• 대한치과기공학회지
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• 제23권2호
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• pp.223-230
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• 2002

Pure titanium and Ti6Al4V alloy have been mainly used as implant materials but the cytotoxicity of V, neurotoxicity of Al resulting in Alzheimer disease had been reported. This paper was described the influence of composition of Ti-Nb alloys with 3 wt%Nb, 20 wt%Nb on the microstructure and corrosion resistance. Specimens of Ti alloys were melted in vacuum arc furnace and homogenized at $1000^{\circ}C$ for 24hr. The alloys were rolled in $\beta$ and ${\alpha}+{\beta}$ regions. The corrosion resistance of Ti alloys were evaluated by potentiodymic polarization test in 0.9% NaCl and 5% HCl solutions. The results can be summarized as follows: 1. The microstructure was transformed from $\alpha$ phase to ${\alpha}+{\beta}$ phase by adding Nb 2. The hardness of Ti-20Nb alloy was greater than Cp- Ti, Ti-3Nb alloy. 3. The corrosion resistance of Ti-20Nb alloy was better than that of Cp-Ti, Ti-3Nb alloy in 0.9%NaCl and 5%HCl solutions.

• Corrosion Science and Technology
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• 제17권3호
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• pp.116-122
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• 2018

The secondary coolant of a nuclear power plant has small amounts of various impurities (S, Pb, and Cl, etc.) introduced during the initial construction, maintenance, and normal operation. While the concentration of impurities in the feed water is very low, the flow of the cooling water is restricted, so impurities can accumulate on the Top of Tubesheet (TTS). This environment is chemically very complicated and has a very wide range of pH from acidic to alkaline. In this study, the characteristics of the oxide and the mechanism of stress corrosion cracking (SCC) are investigated for Alloy 690 TT in alkaline solution containing Pb, Cl, and S. Reverse U-bend (RUB) specimens were used to evaluate the SCC resistance. The test solution comprises 3m NaCl + 500ppm Pb + 0.31m $Na_2SO_4$ + 0.45m NaOH. Experimental results show that Alloy 690 TT of the crevice environment containing Pb, S, and Cl has significant cracks, indicating that Alloy 690 is vulnerable to stress corrosion cracking under this environment.

• Membrane and Water Treatment
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• 제13권4호
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• pp.191-199
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• 2022

In industrial production, the development of traditional polyamide nanofiltration (NF) membrane was limited due to its poor oxidation resistance, complex preparation process and high cost. In this study, a composite NF membrane with high flux, high separation performance, high oxidation resistance and simple process preparation was prepared by the method of dilute solution dip coating. And the sulfonated polysulfone was used for dip coating. The results indicated that the concentration of glycerin, the pore size of the based membrane, the composition of the coating solution, and the post-treatment process had important effects on the structure and performance of the composite NF membrane. The composite NF membrane prepared without glycerol protecting based membrane had a low flux, when the concentration of glycerin increased from 5% to 15%, the pure water flux of the composite NF membrane increased from 46.4 LMH to 108.2 LMH, and the salt rejection rate did not change much. By optimizing the coating system, the rejection rate of Na₂SO₄ and PEG1000 was higher than 90%, the pure water flux was higher than 40 LMH (60psi), and it can withstand 20,000 ppm.h NaClO solution cleaning. When the post treatment processes was adjusted, the salt rejection rate of NaCl solution (250 ppm) reached 45.5%, and the flux reached 62.2 LMH.

• 한국지반공학회지:지반
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• 제13권2호
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• pp.17-28
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• 1997

이 연구에서는 화학액으로서 해안가에서 쉽게 영향 받는 염분을 사용하였다. 염분 용액으로 포화된 모래 벤토나이트 혼합토를 사용하여 압밀 비배수 삼축압축 시험을 실시하였다. 변형과 강도정수를 삼축압축시험을 통하여 구속응력과 염수의 농도 변화에 따라 구하였다. 실험 결과 영수로 포화된 흙과 벤토나이트의 점착력은 염수의 농도가 증가함에 따라 증가하며 내부마찰각은 변화가 없고 탄성계수는 증가하는 것으로 나타났다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.17-18
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• 2021

In the present study, Al-Zn coating was deposited by Arc thermal (AT) and plasma arc thermal (PAT) spray processes, and their corrosion characteristics were studied in 3.5% NaCl through electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM) and mechanical tests. The bond adhesion result showed that plasma arc sprayed coating had a higher value attributed to compact, dense, and less porous coating compared to arc thermal spray coating which contains defects/pores and uneven morphology as revealed by scanning electron microscope analysis. Electrochemical results revealed that the plasma arc sprayed coating had a high polarization resistance at early stage of immersion, suggesting its excellent corrosion protection performance.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.119-120
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• 2023

Corrosion of the steel rebar in coastal environment caused huge economical loss of the globe. Therefore, coating on the steel rebar being used to mitigate the corrosion. In the present study, we have applied epoxy coating on arc thermal sprayed Al coating (a dual metal/polymeric coating) vis-à-vis compared with as coated one (Al coating). The corrosion studies were performed in simulated concrete pore solution with 3.5 wt. % NaCl solution. The morphology of the dual epoxy/Al coating is smooth while Al coating shows rankle and defects. Due to defects, Al coating is susceptible to corrosion while dual epoxy/Al coating has performed excellent compared to as coated one at extended period of immersion.