The electrolytic reduction of a spent oxide fuel involves liberation of the oxygen in a molten LiCl electrolyte, which is a chemically aggressive environment that is too crosive for typical structural materials. Therefore, it is essential to choose the optimum material for the process equipment for handling a molten salt. In this study, the corrosion behavior of pyro-carbon made by CVD was investigated in a molten LiCl-Li2O salt under an oxidation atmosphere at 650˚C and 750˚C for 72 hours. Pyro-carbon showed no chemical reactions with the molten salt because of its low wettability between pyro-carbon and the molten salt. As a result of XRD analysis, pyro-carbon exposed to the molten salt showed pure graphite after corrosion tests. As a result of TGA, whereas the coated layer by CVD showed high anti-oxidation, the non-coated layer showed relatively low anti-oxidation. The stable phases in the reactions were C(S), Li2CO3(S), LiCl(l), Li2O at 650˚C and C(S), LiCl(l), Li2O(S) at 750˚C. Li2CO(S) was decomposed at 750˚C into Li2O(S) and CO2(g).

Coatings composited with alumina and Perfluoro alkoxyalkane (PFA) resin were deposited on stainless steel plate (SUS304) to further improve corrosion resistance. Plate (ca. 10μm) and/or nanosize (27~43 nm) alumina used as inorganic additives were mixed in PFA resin to make alumina-fluoro composite coatings. These coatings were deposited on SUS304 plate with wet spray coating and then the film was cured thermally. According to the amount and ratio of the two kinds of alumina having plate morphology and nano size, corrosion resistance of the film was evaluated under strong acids (HF, HCl) and a strong base (NaOH). The film prepared with the addition of 5~10 wt% alumina powders in PFA resin showed corrosion resistance superior to that of pure PFA resin film. However, for the film prepared with alumina content above 10 wt%, the corrosion resistance did not improve with the physical properties, such as surface hardness and adhesion. The film prepared with plate/nanosize (weight ratio = 1/2) alumina especially enhanced the surface hardness and corrosion resistance. This can be explained as showing that the plate and the nanosize alumina dispersed in PFA resin effectively suppressed the penetration of cations and anions due to the long penetration length and fewer defects that accompany the improved surface hardness under a serious environment of 10% HF solution for over 120 hrs.

순환전압전류법을 사용하여 전류-전압 곡선을 측정하였다. 전기화학적 특성과 금속의 표면상태간의 관계는 전자현미경(SEM)을 사용하여 조사하였다. 그리고 순환전압전류법에 의한 전기화학적 측정은 3 전극 시스템을 사용하였다. 측정 범위는 초기 포텐셜에서 -1350 mV까지 환원시키고, 연속적으로 1650 mV까지 산화시키고, 다시 초기지점으로 환원시켜 측정하였다. 스캔속도는 50, 100, 150, 200 및 250 mV/s를 선정하였다. 그 결과, 부식억제로 모노에탄올아민(MEA)을 사용하여 금속의 C-V 특성은 순환전압전류법으로부터 산화 전류에 기인한 비가역 공정으로 나타났다. 부식억제제로 MEA을 사용하였을 경우에는 전해질의 농도가 증가할수록 확산계수가 감소하는 경향을 나타내었다. 그리고 구리의 SEM 이미지를 보면, 전해질 농도를 증가시키면 표면부식은 증가하였다. 부식억제제로 1.0×10-3M MEA를 첨가시키면, 전해질 농도 0.1 N의 경우 확산계수가 상대적으로 커서 부식억제 효과가 적었다.

염분분위기에서의 부식은 사용후핵연료의 중간저장 기간 동안 304 스테인레스 강재 건식저장용기의 주 열 화기구들 중 하나다. 본 연구에서는 감소정도가 서로 다른 냉연 304 스테인레스 강 시편들에 0.5wt.%의 염화 나트륨 연무를 분사시키면서 느린 변형속도시험(SSRT)과 중성염 분사시험(NSS)을 85℃와 200℃에서 수행하 였다. 85℃에서 2000 시간 동안 시험한 NSS시편의 무게 변화는 200℃에서 시험한 시편의 무게 변화와 크게 달 랐다. NSS 시편의 85℃에서 무게 감량은 미미하였지만, 냉연 감소율이 증가함에 따라서 무게 변화는 점진적으 로 감소하였다. 85℃와 200℃에서 그리고 염분분사 환경에서 가볍게 냉연 가공된 시편의 SSRT 시험으로부터얻은 항복강도와 극한 인장응력의 값은 공기 중의 값보다 약간 낮았다. 그러나 염분 분위기에서 부식으로 인 한 20% 감소 냉연시편의 강도는 더 이상 변화하지 않았다. 예비결과는 냉연 304 스테인레스 강의 질과 성능이 건식저장용기의 제작을 위한 조건에 맞는다는 것을 증명하였다. 그러나 냉연 스테인레스 강의 장기적인 성능 을 더 잘 이해하기 위해서는 염분분위기에서 이 재질의 부식거동에 관한 더 많은 연구가 필요하다.

현재 지구온난화 등의 환경문제로 인해 각종 산업분야에서 정량화에 대한 요구가 증대되어 해양산업에도 그 수요가 증가하고 있는 실정이다. 따라서 본 연구에서는 차세대 경량화 재료인 마그네슘이 활용되기 위해서 반드시 극복해야할 가장 중요한 특성인 내식특성에 대하여 고찰하고, 그 내식특성 향상을 위한 마그네슘 박막의 Morphology나 결정배향성의 영향을 해명하고자 하였다. 실험결과로부터 제작한 Mg 박막의 전기화학적 내식특성은 Ar 가스압이 높은 조건에서 제작한 막일수록 내식특성이 우수하였다. 이러한 경향은 표면 및 단면의 Morphology와 결정배향성과의 상관관계를 통하여 설명 가능하였다.

Simultaneous Ni and C codeposition by electrolysis was investigated with the aim of obtaining better corrosionresistivity and surface conductivity of a metallic bipolar plate for application in fuel cells and redox flow batteries. The carboncontent in the Ni-C composite plate fell in a range of 9.2~26.2at.% as the amount of carbon in the Ni Watt bath and theroughness of the composite were increased. The Ni-C composite with more than 21.6at.% C content did not show uniformlydispersed carbon. It also displayed micro-sized defects such as cracks and crevices, which result in pitting or crevice corrosion.The corrosion resistance of the Ni-C composite in sulfuric acid is similar with that of pure Ni. Electrochemical test results suchas passivation were not satisfactory; however, the Ni-C composite still displayed less than 10−4A/cm2 passivation currentdensity. Passivation by an anodizing technique could yield better corrosion resistance in the Ni-C composite, approaching thatof pure Ni plating. Surface resistivity of pure Ni after passivation was increased by about 8% compared to pure Ni. On theother hand, the surface resistivity of the Ni-C composite with 13at.% C content was increased by only 1%. It can be confirmedthat the metal plate electrodeposited Ni-C composite can be applied as a bipolar plate for fuel cells and redox flow batteries.

In this study, we investigated the C-V diagrams and metal surface related to the electrochemistry characterization of metal(nickel, SUS-304). We determined electrochemical measurement by using cyclic voltammetry with a three-electrode system. A measuring range was reduced from initial potential to -1350mV, continuously oxidized to 1650 mV and measured to the initial point. The scan rate were 50, 100, 150, 200 and 250 mV/s. As a result, the C-V characterization of metal using N,N-dimethylacetamide and N,N-dimethylformamide inhibitors appeared irreversible process caused by the oxidation current from the cyclic voltammogram. After adding organic corrosion inhibitors, adsorption film constituted, and the passive phenomena happened. According to the results by cyclic voltammetry method, it was revealed that the addition of inhibitors containing amide functional group enhances the corrosion resistance properties.

To improve the chemical stability of metal, the ceramic coatings on metallic materials have attracted interest from many researchers due to the chemical inertness of ceramic materials. To endure strong acids, SiOC coating on metal substrate was carried out by dip coating method using 20wt% polyphenylcarbosilane solution; SiC powder was added to the solution at 10wt% and 15wt% to improve the mechanical properties and to prevent cracks of the film. Thermal oxidation as a curing step was carried out at 200˚C for crosslinking of the polyphenylcarbosilane, and the coating samples were pyrolysized at 800˚C under argon to convert the polyphenylcarbosilane to SiOC film. The thicknesses of the SiOC coating films were 2.36μm and 3.16μm. The quantities of each element were measured as SiO1.07C6.33 by EPMA, and it can be confirmed that the SiOC film from polyphenylcarbosilane was formed in a manner that was carbon rich. The hardness of the SiOC film was found to be 3.2Gpa through nanoindentor measurement. No defect including cracks appeared in the SiOC film. The weight loss of the SiOC coated stainless steel was within 2% after soaking in 10% HCl solution at 80˚C for one week. From these results, SiOC coating shows good potential for application to protect against severe chemical corrosion of stainless steel.

Methods of producing hydrogen include steam reforming, electrochemical decomposition of water, and the SI process. Among these methods, the Sulfur iodine process is one of the most promising processes for hydrogen production. The thermochemical sulfur-iodine (SI) process uses heat from a high-temperature-gas nuclear reactor to produce H2 gas; this process is known for its production of clean energy as it does not emit CO2 from water. But the SI-process takes place in an extremely corrosive environment for the materials. To endure SI environments, the materials for the SI environment will have to have strong corrosion resistance. This work studies the corrosion resistances of the Fe-Si, Ni-Ti and Ni Alloys, which are tested in SI-process environments. Among the SI-process environments, the conditions of boiling sulfuric acid and decomposed sulfuric acid are selected in this study. Before testing in boiling sulfuric acid environments, the specimens of Fe-4.5Si, Fe-6Si, Ni-4.5Si, Ni-Ti-Si-Nb and Ni-Ti-Si-Nb-B are previously given heat treatment at 1000˚C for 48 hrs. The reason for this heat treatment is that those specimens have a passive film on the surface. The specimens are immersed for 3~14 days in 98wt% boiling sulfuric acid. Corrosion rates are measured by using the weight change after immersion. The corrosion rates of the Fe-6Si and Ni-Ti-Si-Nb-B are found to decrease as the time passes. The corrosion rates of Fe-6si and Ni-Ti-Si-Nb-B are measured at 0.056 mm/yr and 0.16 mm/yr, respectively. Hastelloy-X, Alloy 617, Alloy 800H and Haynes 230 are tested in the decomposed sulfuric acid for one day. Alloy 800H was found to show the best corrosion resistance among the materials. The corrosion rate of Alloy 800H is measured at -0.35 mm/yr. In these results, the corrosion resistance of materials depends on the stability of the oxide film formed on the surface. After testing in boiling sulfuric acid and in decomposed sulfuric acid environments, the surfaces and compositions of specimens are analyzed by SEM and EDX.

한국원자력연구원 처분시스템개발과제에서는 처분용기 재료로 개발중인 저온분사코팅 구리에 대한 틈새부식(Crevice Corrosion) 시험을 실시하였다. 본 시험을 통하여 틈새에서의 부식의 발생여부와 발생되는 시점인 재부동태 전위(Repassivation Potential)를 측정하고자 하였다. 틈새부식 시험 방법으로 (1) ASTM G61-86 : Cyclic Potentiodynamic Polarization Measurements, (2) SWRI의 PotentiodynamicPolarization plus intermediate Potentiostatic Hold method, 그리고 (3) ASTM G192-08 (THE method) :Potentiodynamic- Galvanostatic -Potentiostatic Method 등의 3가지 방법을 소개하였다. 실제 저온분사코팅구리의 부식시험에서는 ASTM G61-86에 따라서 틈새부식장치를 설치하고, 저온분사 코팅구리가 KURT 지하수를 모사한 용액에서 어떻게 틈새부식이 일어나는지 살펴보았다. 전기적 부식조건으로는 Cyclic Polarization Test, Potentiostatic Polarization Test, 및 Electrochemical Impedance Spectroscopy등을 사용하였다. 그리고 부식이 된 시편에 대해 Profilometer Measurement를 통해 실제 부식표면의 높낮이를 조사하여 틈새부식 유무를 관찰하였다. 최종적인 결론에서는 저온분사코팅구리는 틈새부식을 나타나지 않는다는 것을 확인할 수 있었다. 그리고 시험에 사용된 세종류의 구리에 대한 상대적인 부식평가를 한 결과, 부식전위를 나타내는 개방회로(Open Cell)에서의 전위는 구리의 제조방식과 상관없이 구리의 순도가 높을수록 높은 값을 보이는 것을 확인할 수 있었다. 결론적으로 KURT 심층지하수 조건에서는 구리는 틈새부식이 발생되지 않는다고 결론지었다.

A study on the corrosion inhibition of metals is important in many industrial applications (carbon steel, copper, aluminum, SUS 304, nickel). In this study, we investigated the C-V diagrams related to the surface corrosion of metals. It was observed through the SEM that the surface corrosion state of the various metals had the corrosion potential by the scan rate and the organic inhibitor containing an amine group. We determined to measure cyclic voltammetry using the three-electrode system. The measurement of oxidation and reduction ranged from -1350mV to 1650mV. The scan rate was 50, 100, 150, and 200mV/s. It turned out that the C-V characterization of SUS 304 was irreversible process caused by the oxidation current from the cyclic voltammogram. After adding organic inhibitors, the adsorption film was constituted, and the passive phenomena happened. As a result, it was revealed that the inhibition effect of metal corrosion depends on the molecular interaction, and the interaction has influence on the adsorption complex.

Chromium nitride (CrN) samples with two different layer structures (multilayer and single layer) were coated on bipolar plates of polymer electrolyte membrane fuel cells (PEMFC) using the reactive sputtering method. The effects with respect to layer structure on corrosion resistance and overall cell performance were investigated. A continuous and thin chromium nitride layer (Cr0.48 N0.52) was formed on the surface of the SUS 316L when the nitrogen flow rate was 10 sccm. The electrochemical stability of the coated layers was examined using the potentiodynamic and potentiostatic methods in the simulated corrosive circumstances of the PEMFC under 80˚C. Interfacial contact resistance (ICR) between the CrN coated sample and the gas diffusion layer was measured by using Wang's method. A single cell performance test was also conducted. The test results showed that CrN coated SUS316L with multilayer structure had excellent corrosion resistance compared to single layer structures and single cell performance results with 25 cm2 in effective area also showed the same tendency. The difference of the electrochemical properties between the single and multilayer samples was attributed to the Cr interlayer layer, which improved the corrosion resistance. Because the coating layer was damaged by pinholes, the Cr layer prevented the penetration of corrosive media into the substrate. Therefore, the CrN with a multilayer structure is an effective coating method to increase the corrosion resistance and to decrease the ICR for metallic bipolar plates in PEMFC.

산화물 사용 후 핵연료를 처리하는 전해환원공정에서는 LiCl 용융염계에서 산소가 생성되는 반응을 수반하게 되 며, 생성된 산소로 인해 반응기의 구조재료를 상당히 부식시킬 수 있는, 화학적으로 심각한 반응환경을 조성한다. 따라서, 고온 용융염을 다루는 전해환원 공정장치를 위해서는 최적의 재료를 선택하는 것이 필수적이다. 본 연구에 서는 리튬용융염, 675℃, 216시간동안 산화분위기에서 코팅이 안 된 초합금과 코팅된 초합금 시편의 고온 부식연구 를 수행하였다. IN713LC 초합금 시편에 aluminized NiCrAlY bond 코팅 후 Y2O3 top 코팅을 하였다. 코팅이 안 된 초 합금은 부식층의 빠른 성장응력과 열적응력에 의한 부식층의 박리로 명확한 무게손실을 보인다. 탑 코팅의 화학적 및 열적 안정성으로 인해 고온 리튬용융염을 다루는 구조재료의 부식 저항성이 증가함을 확인할 수 있었다

Benzotriazole (B.T.A) which has been mainly used for the stabilization processing method of excavated copper and bronze artifacts is vaporized within 2~3 years after the usage because it is unstable at the acid conditions and cannot protect the surface of artifacts. In this study, NaOH method which has been used for the steel artifacts was applied as a stabilization process for the method of copper and bronze artifacts to gush chlorine ion out. For the reproduction of excavated samples, copper and bronze plates were dipped in 0.1M HCl for 26 hrs to form CuCl, rusted at 70˚C with RH 75% for the formation of corrosion products, and desalted in 0.1 M NaOH solution. The concentration of chlorine ion was measured by using ionchromatography. During the desalting process, a large quantity of chlorine ions was gushed out in early period and corrosion products were not additionally generated through the re-corrosion experiment. This NaOH desalting process was found to be a method of stabilization process for copper and bronze artifacts from the formation of Tenorite (CuO) during desalting as a protection layer for corrosion.

The acrylic coating emulsions were prepared by the emulsion polymerization to protect the surface of steel plate from the corrosion chemicals like acid, base and salt water. MMA(methyl methacrylate), styrene, BA(butyl acrylate), and 2-HEMA(2-hydroxyethyl methacrylate) were used as monomer. KPS(potassium persulfate) and SBS(sodium bisulfite) as redox initiator and SDBS(sodium dodecylbenzene sulfonate) as emulsifier were used on the emulsion polymerization reaction. The most stable in-situ coating was obtained when 10% of MMA was added. Both particle size and quantity in emulsion were decreased as increasing the mount of SDBS. the most stable prepared coating emulsion with polyisocyanate crosslinker showed very high anticorrosion properties on the coated steel layer to salt water, whereas no significant improvement of anticorrosion property to acdic and basic condition it showed.