The purpose of this study was to examine whether galvanic corrosion of copper occurs by inserting a third barrier layer with a higher corrosion potential than copper between copper and cast iron when the copper layer is locally perforated by pitting or partial corrosion. A triple layer composed of copper, inserted metal, and carbon steel was manufactured by cold spray coating of inserting metal powders such as Ag, Ni, and Ti on carbon steel plate followed by Cu coating on it. First, the corrosion properties were evaluated electrochemically for each metal coating. As a result of Tafel plot anaylsis in KURT groundwater condition, the corrosion potential of Fe (-567 mV) was much lower than that of Cu (-91 mV), and the corrosion potential of Ni (-150 mV) was also lower than that of Cu. Therefore, Ni was likely to corrode before Cu. However, the corrosion current of Ni was lower than that of the Cu. In the galvanic specimen where the copper and inserting metal were exposed together, Cu-Fe was much lower corrosion potential of -446 mV, and the corrosion potential of Cu-Ti, Cu-Ni, and Cu-Ag were slightly higher than that of Cu. Therefore, it seemed that Ag, Ni, and Ti all might promote galvanic corrosion of surrounding copper when the copper layer was perforated to the inserted metal layer. If the metal insertion presented in this study operates properly, the disposal container does not need to worry about the partial corrosion or non-uniform corrosion of external copper layer.

Long-term safe storage of spent nuclear fuel (SNF) determines sustainability of the current light water reactor (LWR) fleet. In the U.S., SNF is stored in stainless steel canister in dry cask storage system (DCSS) after spending several years in wet pool storage system while there is no DSCC in Republic of Korea. The SNF storage time in DSCC is expected to be multiple decades since no permanent geological repositories are identified in both countries. One limiting factor for extended storage of SNF in DSCC is chloride-induced stress corrosion cracking (CISCC) in the welded regions of the stainless steel canisters. The propensity for the occurrence of CISCC has warranted the development of the mitigation and repair technologies to ensure the safe and long-term storage for both present and new canister although no CISCC failure was reported yet. This study investigates cold spray deposition coatings of 304 L and 316 L stainless steels on prototypical stainless steel canisters such as sensitized flat and C-ring samples. The cold spray technology has been identified as the most promising approach by Extended Storage Collaboration Program (ESCP) driven by Electric Power Research Institute (EPRI). The talk includes microstructural characterization, adhesion strength measurement, residual stress evaluation, and corrosion behavior of the coated materials in boiling MgCl2 solution and electrochemical corrosion tests in NaCl solution. In addition, the capability of repair of cracks on the canister surface using the coating technology will be presented.

In this paper, graphene-coated Al powders prepared by in situ reduction method were directly used for cold spraying, obtaining a graphene-reinforced Al matrix composite coating with more compact structure and better performance. Cross-sectional analysis revealed that compared with the pure Al powders, the graphene-coated Al powders were more severely deformed, and the resulting coating was denser and its porosity was reduced by over 80%. The hardness of the graphene-coated Al coating was increased by 40%, and its brine immersion time was prolonged by nearly three times. However, the graphene increases the pitting sensitivity of the Al coating; so, the enhanced corrosion resistance of the graphene-coated Al coating is mainly attributed to the improvement of its structure densification.

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.

Metal/diamond binary composite coatings on Al substrate without grit blasting were deposited by cold spray process with insitu powder preheating. Microstructural characterization of the as-sprayed coatings with different diamond size, strength and with/without Ti coating on diamond was carried out by OM and SEM. The assessment of basic properties such as tensile bond strength and hardness of the coatings, and the deposition efficiency was also carried out. Particular attention on the composite coatings was on the diamond fracture phenomenon during the cold spray deposition and the interface bonding between the diamond and the Fe-based metal matrix.