• 한국응용과학기술학회지
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• 제24권4호
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• pp.399-409
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• 2007

Characteristics of polyaniline anti-corrosive coatings with various primer coating resins(epoxy resin, urethane resin, and others) and top coating resins(epoxy and acrylic urethane resins) were investigated through adhesion, acid resistance, alkaline resistance, water resistance, and anti-corrosion tests. As a result, the anti-corrosive properties of the prepared coatings using polyaniline varied with the types of primer and top coating resins. In this condition, the properties of adhesion, chemical resistance, and water resistance were found to be very satisfactory when using emeraldine base (EB) of polyaniline blended with single-packaged urethane and acrylic urethane resins as the primer coatings, and using acrylic urethane resin as the top coatings. Also, the anti-corrosive function of these anti-corrosive coatings was well preserved for 1000 hr in the salt spray experiment.

• 한국지반공학회논문집
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• 제20권2호
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• pp.27-36
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• 2004

극성저항 계측법과 전기화학 임피던스 분광학을 이용하여 영구적 지반 앵커의 부식율을 계측하는 절차를 제시하였다. 극성저항 계측법을 이용하여 대표지반의 종류와 철의 부식률에 관한 특성관계를 도출하였고, 전기화학 임피던스 분광학을 이용하여 시간의존 부식 반응과 다양한 종류의 코우팅 시스템의 평가, 그리고 시멘트 그라우팅이 부식에 미치는 영향에 대하여 각각 평가하였다. 실험 결과 점성토와 사질토의 pH 지수가 5이하인 경우 부식발생이 용이한 지반으로서 영구적 지반 앵커의 부식반응에 심각한 영향을 미치리라 판단된다. 또한 중성 또는 알카리성의 지반은 부식진행이 관찰되지 않았으며 부식률은 pH지수에 관계없이 일정한 결과를 보였다. 포설린 점성토의 경우 pH지수의 변화가 철의 부식에 매우 낮은 영향을 미쳤다. 한편 시멘트 그라우팅의 사용은 철의 부식율을 약 0.003-0.0lmm/y 정도로 낮출 수 있었으며 에폭시 혼합 코우팅의 경우도 부식의 영향을 받지않고 원 상태를 유지할 수 있어 매우 효과적으로 부식효과를 감소시킬 수 있었다.

• 한국표면공학회지
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• 제47권4호
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• pp.147-154
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• 2014

Formation behavior of PEO (Plasma Electrolytic Oxidation) films on AZ31 Mg alloy was studied in aqueous solutions containing various concentrations of hydroxide ion ($OH^-$) and silicate ion ($SiO_3{^{2-}}$) by voltage-time curves, and corrosion resistance of the PEO film-covered specimen was investigated by immersion test in 0.5 M NaCl solution. From the analyses of the voltage-time curves, it is suggested that two different types of anions are essentially needed for the formation of PEO films on AZ31 Mg alloy: film formation agent and local film breakdown agent. $SiO_3{^{2-}}$ ion acts only as a film formation agent but $OH^-$ ion acts not only as a film formation agent but also film breakdown agent. The PEO films prepared on AZ31 Mg alloy in alkaline silicate solution showed very good corrosion resistance without any pitting or filiform corrosions up to 480 h of immersion in 0.5 M NaCl.

• 한국표면공학회지
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• 제44권2호
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• pp.44-49
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• 2011

The films formed on AZ31B magnesium alloy were prepared from alkaline solution composed of potassium permanganate and sodium hydroxide. The immersion tests were carried out at the different concentration of sodium hydroxide and pre-treatment method in 5 minute. The morphology and the phase composition of the film were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion behavior of the film in 5.0% NaCl solution was evaluated using potentiodyanmic polarization. Open circuit potential in developing film was examined with time. The thin and transparent film was mainly composed of MgO and $Mg(OH)_2$. The film with the best corrosion resistance was obtained at $70^{\circ}C$ bath temperature, 1.6 M concentration of sodium hydroxide and chemical pre-treatment.

• 한국표면공학회지
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• 제52권3호
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• pp.117-122
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• 2019

In this study, surface porosity and corrosion resistance of PEO coatings prepared on the 6061 Al alloy were investigated in terms of sodium phosphate ($Na_3PO_4$) concentrations in an alkaline solution and $NaAlO_2$ sealing. The surface morphologies of the PEO coatings clearly show that the coatings film formed in $9g\;L^{-1}$ had the lowest porosity. The $NaAlO_2$ sealing was found to remove micropores and cracks existing on the surface of PEO coatings. As a result, the $NaAlO_2$ sealing resulted in the movement of corrosion potential toward more positive value and lower corrosion current density.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1518-1527
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• 2023

A method was proposed for in-situ evaluating the thickness and resistivity of the oxide/hydroxide film formed on the surface of aluminum alloy exposed to sump water formed in the containment after a loss-of-coolant accident. The evaluation entailed fitting a model for the film impedance, which has film thickness and other variables describing the resistivity profile of the film along its thickness direction as fitting parameters, to the practically measured electrochemical impedance data. The obtained resistivity profiles implied that the films formed at pHs_25℃ 7, 8, 9, 10, and 11 all had a duplex structure; compared to the outer layer in contact with the solution, the inner layer of the film had a much higher resistivity and was inferred to be denser and provide most of the protectiveness of the film. Both the thickness and the total resistance of the film decreased with the increasing solution pH_25℃, suggesting that the films formed in more alkaline solutions had less protectiveness against corrosion, consistent with the increasing aluminum alloy corrosion rates previously identified.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1996년도 재료학회 추계학술발표회
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• pp.12-12
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• 1996

• Corrosion Science and Technology
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• 제14권4호
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• pp.166-171
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• 2015

Knowledge of how metal releases from the stainless steels used in food processing applications and cooking utensils is essential within the framework of human health risk assessment. A new European standard test protocol for testing metal release in food contact materials made from metals and alloys has recently been published by the Council of Europe. The major difference from earlier test protocols is the use of citric acid as the worst-case food simulant. The objectives of this study were to assess the effect of citric acid at acidic, neutral, and alkaline solution pH on the extent of metal release for stainless steel grades AISI 304 and 316, commonly used as food contact materials. Both grades released lower amounts of metals than the specific release limits when they were tested according to test guidelines. The released amounts of metals were assessed by means of graphite furnace atomic absorption spectroscopy, and changes in the outermost surface composition were determined using X-ray photoelectron spectroscopy. The results demonstrate that both the pH and the complexation capacity of the solutions affected the extent of metal release from stainless steel and are discussed from a mechanistic perspective. The outermost surface oxide was significantly enriched in chromium upon exposure to citric acid, indicating rapid passivation by the acid. This study elucidates the effect of several possible mechanisms, including complex ion- and ligand-induced metal release, that govern the process of metal release from stainless steel under passive conditions in solutions that contain citric acid.

• 한국지반공학회논문집
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• 제36권8호
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• pp.27-34
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• 2020

터널시공 현장에서는 콘크리트와 숏크리트 및 각종 그라우팅 공법의 사용으로 다량의 알칼리성 폐수가 발생되고 있으며 하천오염을 방지하기 위해 중성화 처리를 해서 방류해야 한다. 현재는 이를 황산과 같은 강산으로 중화 처리하고 있으나 취급상의 위험이 내재 되어있다. 그 대안으로 이산화탄소(CO₂) 사용이 부각되었고 다양한 실내실험 연구가 진행되어 그 가능성이 입증되고 있다. 하지만 아직 CO₂의 현장 적용연구가 절대 부족하고 특히 건설현장에서는 실내 실험 결과와는 다른 특성을 보이고 있기 때문에 현장 적용이 어려운 실정이다. 이에 본 연구에서는 현장 실험을 통하여 실제 현장 적용 가능성을 검증하고자 한다.

• Nuclear Engineering and Technology
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• 제27권4호
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• pp.453-462
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• 1995

사용후 핵연료 저장구조재의 구조적 안정성자 관련해서, 감마선 조사 생성물로 알려져 있는 $H_2O$$_2$를 전해질에 주입시키었을 때, $H_2O$$_2$가 저장구조재인 304L스텐리스강의 부식거동에 어떤 영향을 미치는가를 조사하였다. 실험결과, $H_2O$$_2$는 304L 스텐리스강의 부식전위를 상승시키고 Pitting 전위를 감소시킴으로써 부동태 영역을 줄이고 pitting 저항성을 감소시키는 것으로 나타났다. 이는 감마선 조사에 의한 부식 거동 변화와 유사한 결과라고 볼 수 있으며, 또한 산소농도증가에 의한 부식거동 변화와 유사한 결과로 해석되었다. 재부동태형성전위가 $H_2O$$_2$의 존재로 증가하는데, 이로써 응력부식균열임계전위는 약간 상승할 것으로 추론되었다. 그러나, $H_2O$$_2$ 농도가 6.3$\times$$10^{-6}$M 이하로 떨어질 경우, $H_2O$$_2$는 부식거동에 영향을 주지 못했다. 이는 대기압상태에서 용존된 $O_2$환원반응속도에 비해 $H_2O$$_2$환원반응속도가 작기 때문이라고 해석되었다. 중성용액보다 산성 및 염기성 용액에서, $H_2O$$_2$가 부식거동에 미치는 영향이 작아졌는데, 이는 산성용액에서는 높은 H$^{+}$ 농도 때문에, 염기성용액에서는 le Chatelier의 원칙 때문인 것으로 해석되었다.