Electrodeposited NiMo Alloy Coatings for Improved Corrosion and Erosion Resistance in Extreme Environments

The use of molten fluoride salts as a primary coolant within next generation nuclear reactors has the potential to improve efficiency and nuclear reactor safety by operating at low pressures and high temperatures without boiling. However, these coolants will require the development of new corrosion resistant material systems that will have to meet or supersede existing standard codes for these systems. Therefore, state of the art reactors require validation and testing of new material systems that can produce robust component structures and enable them to withstand these corrosive environments. Furthermore, any next generation process to apply protective coatings must allow for a conformal, thick, dense, and bonded materials to be formed onto any low cost ASME material (like 316H SS) that comprises the structure of heat exchanger and containment vessel components.

Within this context, Faraday Technology Inc. is working on developing low cost and high value corrosion-resistant alloy coatings for next generation molten salt reactors with the goal of increasing their functional lifetime, while reducing the component cost. The manufacturing process involves electrodeposition of functionally graded NiMo alloys onto ASME certified substrates and subsequent high temperature corrosion evaluation in molten fluoride salt electrolytes. A wide array of electrolytes and processing parameters were evaluated in order to understand these effects on the deposit composition, structure, and corrosion resistance properties towards the goal of developing an ideal alloy coating. Specifically, we demonstrated the potential to apply graded NiMo coating to the 316H SS surface and found that a coating composition of ~25% Mo has the potential to improve the components lifetime.