Corrosion Behavior of Metallic Alloys in a Molten Chloride Eutectic Salt

摘要

There is an ongoing need to develop methods of energy production that are high-yielding, cost efficient, and clean alternatives to fossil fuels. The depletion of coal and oil resources is leading to a gradual decline in the implementation of these methods, and cleaner approaches to energy production are preferred. Nuclear power is one option that has the potential to resolve these issues. Other alternative energy sources such as solar energy and wind energy exist, but their cost of operation and maintenance can cause these processes to be more expensive than the nuclear approach in the long term. There appears to be a shift towards molten salts as a coolant in place of water in the nuclear sector. The use of molten salts provides greater energy storage when compared to water, albeit accompanied by potential increases in corrosion risks. This alternative also eliminates the risk of explosion, since molten salts do not require containment in pressurized vessels and do not react chemically with nearby materials. Fluoride salts are the preferred candidates for this application, but the associated expenses and safety hazards make them unappealing for prolonged utilization. A safer and more cost-effective alternative must be considered. Chloride salts fulfill these requirements, but they are highly corrosive. Therefore, deliberation is required in the selection of their containment vessel material. In this project, two stainless steels (UNS S31600 and UNS S30400) and one nickel-base alloy (UNS N06601) were tested at 700°C in a ternary molten eutectic (LiCI-KCI-MgCI_2 ) salt. The progression of corrosion was measured using immersion techniques following the ASTM G1-03 standard. The post-test coupons were categorized with optical microscopy and scanning electron microscopy (SEM). The viability of the chloride-salt as a replacement for the currently used fluoride salts and the effects of the molten salt on the tested alloys are discussed based on the results from this study.