In this study, a milled carbon nanofiber-reinforced composite paint was prepared to enhance the anti-corrosive properties of concrete structures. Shorter-length (40 μm) milled carbon fibers (MCFs) showed an increased viscosity relative to longer MCFs (120 μm) owing to their 2 weeks (the decrease was especially strong in the acid solution). A carbon nanotube (CNT)- reinforced composite paint showed similar results in uniform distribution in the epoxy resin. The latter showed a decrease in viscosity owing to agglomerative movement in the epoxy resin. The surface hardness and tensile strength of the composite paint linearly increased as the carbon nanofiber loading was increased by up to 7.2 wt% in the epoxy resin, and slowly decreased after soaking in a sulfuric acid or sodium hydroxide solution for to those of the MCFs, whereas CNTs dispersed in isopropyl alcohol (IPA) in advance and mixed with resin showed lower hardness values than those without dispersion in IPA at the same loading. The mechanical properties such as the Shore D hardness and tensile strength of the MCF-reinforced composite paint increased significantly, resulting in a slower surface degradation of the composite paint concrete in a sulfuric acid and sodium hydroxide solution.

Viscosity is a fundamental physical property that is important in any system in which fluid movement occurs. In addition, most of the elements exist as ions in molten state in high-temperature molten salt, and electrical conductivity in such molten state is closely related to viscosity as a transport property. Molten salt reactor (MSR) and pyroprocess are representative processes dealing with high-temperature molten salts, actinide elements, and other radioactive materials. In MSR and pyroprocesses, the viscosity data must be provided as one of the fundamental physical property data required for safe process operations and countermeasures to severe accidents. In order to measure the viscosity of highly corrosive molten salt at high temperatures, we have built a in-house developed molten salt viscosity measurement system based on the Brookfield rotationary viscometer. We also developed a special correction technique to improve the accuracy of the viscosity measurement. In this study, the viscosity was measured at 500°C for NaCl-MgCl2 molten salt, which is selected as the base salt material of MSR system under development in Korea Atomic Energy Research Institute (KAERI), using our viscosity measurement system installed in a oxygen- and moisture-free Ar-atmosphere glovebox. Our viscosity measurement system was calibrated using a LiCl-KCl eutectic mixture with well-known viscosity value, and viscosity values obtained using our own correction methodology were compared with those of other conventional correction methods. In our further study, we plan to measure the NaCl-MgCl2-UCl3 system at various compositions and temperatures.

Two waste forms, namely cement and geopolymer, were investigated and tested in this study to solidify the corrosive sludge generated from the surface and precipitates of the tubes of steam generators in nuclear power plants. The compressive strength of the cement waste form cured for 28 days was inversely proportional to waste loading (24.4 MPa for 0wt% to 2.7 MPa for 60wt%). The corrosive sludge absorbed the free water in the hydration reaction to decrease the cementation reaction. When the corrosive sludge waste loading increased to 60wt%, the cement waste form showed decreased compressive strength (2.7 MPa), which did not satisfy the acceptance criteria of the repository (3.45 MPa). Meanwhile, the compressive strength of the geopolymer waste form cured for 7 days was proportional to waste loading (23.6 MPa for 0wt% to 31.9 MPa for 40wt%). The corrosive sludge absorbed the free water in the geopolymer when the water content decreased, such that a compact geopolymer structure could be obtained. Consequently, the geopolymer waste forms generally showed higher compressive strengths than cement waste forms.

In aluminum brazing processes, corrosive flux, which is used in preventing oxidation, is currently raising environmental concerns because it generates many pollutants such as dioxin. The brazing process involving noncorrosive flux is known to encounter difficulties because the melting temperature of the flux is similar to that of the base material. In this study, a new brazing filler material is developed based on aluminum and non-corrosive flux composite powder. To minimize the interference of consolidation aluminum alloy powder by the flux, the flux is intentionally embedded in the aluminum alloy powder using a mechanical milling process. This study demonstrates that the morphology of the composite powder can be varied according to the mixing process, and this significantly affects the relative density and mechanical properties of the final filler samples.

Applicability of corrosion inhibitor was evaluated using pilot scale water distribution pipe simulator. Calcium hydroxide was used as corrosion inhibitor and the corrosion indices of the water were investigated. Corrosion indices, Langelier saturation index (LI) increased by 0.8 and calcium carbonate precipitation potential (CCPP) increased by 9.8 mg/L. This indicated that corrosivity of water decreased by corrosion inhibitor and the effects lasted for 18 days. Optimum calcium hydroxide dose was found to be 3~5 mg/L for corrosion inhibition. We suggest that monitoring of CCPP as well as LI need to be conducted to control corrosivity of water.

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.

Anti-corrosive coatings for steel structures with an alternative anti-corrosive pigment, polyaniline was prepared and anti-corrosive characteristics of the prepared coatings were investigated. The structure of the polyaniline was identified by using FT-IR, UV/Vis. and TGA analysis, and the anti-corrosive properties were analyzed from the results of the salt spray experiment. We found that the anti-corrosion properties of the prepared coatings varied in accordance with the types of primer coating resins as well as with the existence and nonexistence of the top coating. In this condition, the properties of adhesion, chemical resistance, and water resistance were found to be very satisfactory when using the single-packaged urethane resin as the primer coating resin and the urethane resin as the top coating resin.

The marine structures with sea water cooling system always expose to the oceanic atmosphere. Therefore, the protection of the equipments is very important. To investigate the effectiveness of advanced composite materials for the application in offshore environments, the tensile test, hardness test, undercutting property test, permeance test and the friction and wear test were carried out by using various applicable coating materials. The main results obtained can be summarized as follows; 1. The micro-hardness of the Archcoat 502B showed the highest value. 2. The coefficient of friction of the Rigspray coating at the speed of 2.21m/sec showed the lowest value, and that of the Archcoat 502B coating at 1.08m/sec and 0.18m/sec indicated the lowest values. 3. The wear mass at the speed of 0.18m/sec and 1.08m/sec in dry condition showed the smallest values. 4. The Archcoat 502B coating is fitted to the dynamic instruments in the range of low speed and middle speed. Rigspray coating is fitted to the dynamic instruments in the range of high speed. 5. The wear mass of five kinds of coating materials at the range of low speed was very small, and those of the Archcoat S02B, Archcoat 402B and Rigspray coating at high speed range were quitely smaller than those of the Modified Epoxy and Tar Epoxy.

Raw and secondary waste materials from recycling products have been used to produce cements. A total of 10 cements produced from recycling products were analyzed for chemical composition, such as Na2O, MgO, Al2O3, SiO2, SO3, Cl, K2O, CaO, TiO2, Cr2O3, MnO, Fe2O3, CuO, ZnO, and PbO, using the Korean standard leaching test. The total content of toxic substances, such as Pb, Cd, Cu, As, Hg, and Cr(VI), present in each cement was also measured. The corrosion characteristics of cement leachates were also determined by measuring their pH values using an ion selective electrode and measuring the corrosion rate of a circular steel plate in each leachate. The chemical composition of the cements was found to be 60-67% CaO, 18-23% SiO2, and 5-6% Al2O3. Based on the results of the leaching tests, the samples did not exceed the prescribed regulatory leaching levels. The total content of toxic substances in each cement did not exceed the voluntary agreement criteria of 20 mg/kg. In the case of the corrosion characteristics of the cement leachates, the pH of each leachate was greater than 12.5 and the corrosion rate of a circular steel plate in each leachate did not exceed 6.35 mm/yr. The correlation between pH and the corrosion rate of steel in the solid waste leachates was difficult to determine.

A total of 15 different solid waste materials were analyzed for toxic substances such as Pb, Cd, Cu, As, Hg, Cr (VI)by the Korean standard leaching test and as total content. These wastes were also tested for corrosivity characteristicsusing an ionic electrode for pH and a circular steel for corrosion rate. Based on the results of the leaching test, the solidwaste samples did not exceed the regulated leaching levels. Thus, the analyzed wastes may be classified and managedas general industrial waste, not hazardous waste. Four solid waste samples were greater than total content levels proposedby other previous study. In case of the corrosive property of the solid waste leachate (1:2.5), the highest pH of the wastesample exhibited the lowest corrosion rate of 0.065mm/yr. However, the waste samples with low pH values exhibiteda greater corrosion rate. It is difficult to determine the correlation between pH and corrosion rate of the solid waste leachate.Therefore, the testing of the solid wastes are needed to further investigate the corrosion of a glass electrode method ratherthan the corrosion rate measurement. In the future, other hazardous properties such as ecotoxicity should be also examinedto properly manage the solid waste materials.

The tap water is generally known to be corrosive in the pH range at 6.5 ~ 7.5. And the degree of corrosion varies depending on the types of raw water such as river surface water or lake water of the dam. Although several corrosion index represents the corrosivity of tap water, the typical corrosion indexes such as Langelier saturation index (LI) and calcium carbonate precipitation potential (CCPP) were calculated to monitoring the corrosive water quality about raw and tap water in water distribution system. To control the corrosive water quality, the correlation between corrosion index and water quality factors were examined. In this study, corrosion index (LI, CCPP) and the pH was found to be most highly correlated.

방사성 폐기물을 지하에 장기 보관하는 금속 용기에 관한 생지화학적 부식 특성을 알아보기 위해 주철과 구리로 된 금속재료를 환원조건 하에서 디설프리칸스 황산염환원미생물과 3개월간 반응시켰다. 금속재료의 화학적/광물학적 변화를 알아보기 위해 주기적으로 용존 금속이온들의 농도를 측정하였으며, 실험이 종료된 이후 금속 시편 및 표면 이차생성물들을 전자현미경을 이용하여 분석하였다. 디설프리칸스가 없는 조건에서는 금속재료의 부식이 매우 미약하였으나, 미생물이 있는 경우에는 부식이 상대적으로 컸다. 관찰된 생지화학적 부식 산물은 주로 맥키나와이트와 황화구리 같은 검은색의 금속황화물이었으며, 표면에서 쉽게 분리되거나 콜로이드화되어 부유하였다. 특히, 구리 시편의 경우 용액 상에 용존 철이 존재할 때 세균에 의한 구리 부식의 가속화가 관찰되었는데, 이는 구리 표면에 다른 종의 황화철이 성장하면서 구리 간의 결속력을 약화시켰기 때문인 것으로 보인다.

비파괴 기법중 반전위 측정법은 부식가능성을 정량적으로 판별할 수 있으므로 꾸준하게 사용되고 있다. 본 연구에서는 피복두께를 10, 30, 60mm, 물-시멘트비를 0.35, 0.55, 0.70으로 변화시킨 RC 시편을 대상으로 비말대 지역을 모사한 촉진염해분무실험을 수행하였다. 45일간의 촉진 염해 분무시험을 수행한 뒤, RC 시편에 대하여 반전위값을 측정하였다. w/c 0.55 조건에서 피복두께가 10mm인 RC 시편은부식이 발생하였으며, w/c 0.7인 경우 피복두께 30mm인 시편에서도 부식이 발생하였다. 실험결과를 이용하여 물-시멘트비와 피복두께를 변수로 하는 반전위 평가식을 제안하였으며, 비말대지역에서 부식을 억제할 수 있는 조건을 도출하였다. 또한 Life 365 프로그램을 이용하여 비부식 조건의 w/c와 피복두께를 분석하였으며, 본 연구의 결과인 반전위 측정값과 비교하였다.

해수에 노출된 콘크리트 구조물은 시간의 경과에 따라 철근부식이 야기될 수 있으며, 이는 구조적인 성능저하로 진전된다. 1단계 연구에서 도출된 해수전착시스템의 개발을 통하여 2단계 연구에서는 해수전착 코팅된 철근 및 코팅철근을 사용한 RC 콘크리트 부재의 구조적, 내구적 성능이 평가되었다. 내구적 성능평가에서는 반전위 측정이 수행되었는데, 코팅된 철근은 일반철근의 35%수준의 부식속도를 가지고 있었으므로 높은 내부식성을 확보하고 있었다. 구조실험에서는 직접인장시험, 부착력시험, RC 부재를 이용한 휨 및 전단시험이 수행되었다. 인장강도 시험에서는 3.2%, 부착성능에서는 8.8%의 강도 증가가 코팅된 철근에서 평가되었다. RC보에 대한 실험에서는 최대하중 및 파괴형태는 두가지 경우에서 거의 동일하게 평가되었다. 해수전착된 시편은 철근주위에 콘크리트와 비슷한 화합물(수산화마그네슘, 탄산칼슘)이 형성되므로 부착력 및 강도를 일부 증가시키는 것으로 평가되었다. 해수전착철근은 피로, 내충격성, 장기침지실험 등을 통하여 성능이 입증되면 더욱 활발하게 사용될 것으로 사료된다.

본 연구는 해수에 존재하는 다량의 칼슘 및 마그네슘 이온을 전기적으로 강판에 전착하는 전착시스템을 개발하는 것이다. 최종적인 목표는 해수를 이용하여 전착한 구조용 철근의 개발이며, 본 연구는 1단계 연구로서 고내구성 철근개발을 위한 전착시스템 개발에 목적을 두었다. 다양한 전극과 온도, 전류밀도, 코팅시간 등을 변수로 하고 실험을 수행하여 철근 코팅을 위한 최적의 조건을 도출하였다. 탄산칼슘(CaCO3)과 수산화마그네슘(Mg(OH)2)으로 구성된 코팅층은 SEM, EDS, XRD 등을 통하여 성분을 파악하였으며, 자연전위 및 전류밀도를 분석하여 기존의 철보다 부식에 대하여 매우 안전함을 확인하였다. 본 연구의 성과를 이용하여 고내구성 강재의 구조적, 내구적 실험에 대한 토의가 2차 연구에서 추가적으로 수행될 것이다.