Corrosion
Fluoride salts, like all salts, cause corrosion in most metals and alloys. There are three mechanism through which they can cause corrosion: impurities in the salt, temperature gradients in the salt system, and chemical activity gradients. O2, H20, and all oxides are the main impurities that cause corrosion through the following reactions:
All of these reactions work together to create hydrofluoric acid which is highly corrosive to many metals. All of these reactions can be reversed by adding a combination of hydrogen gas and hydrofluoric to the molten salt yielding water, which can be boiled off. This process is accelerated by the high temperatures encountered in a nuclear reactor and is one of the main problems in a molten salt reactor. Some compounds, such as the nickel-based Hastelloy-N were engineered specifically for the molten salt reactor experiment and proved highly resistant to corrosion by molten fluoride salts.
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