US Lab Studies Coatings for Solar Energy Storage


A researcher at the National Renewable Energy Laboratory—run by the U.S. Department of Energy—is working on developing nickel-based coatings that could help to protect concentrating solar power plants from corrosion caused by molten salts that are part of the power-storage process.

Concentrating solar power facilities store power that was generated by the sun by converting concentrated solar energy into thermal energy. The process uses high-temperature fluids, including molten salts, though, and that can wreak corrosive havoc on metal piping, heat exchangers and other equipment.

Hot Salt Solutions

Right now, CSP uses molten salt mixtures containing sodium chloride, potassium chloride and magnesium chloride, according to NREL. These fluids, operating at upward of 1,000 degrees Fahrenheit, are eating away at stainless steel surfaces at a rate, in some cases, of more than 200 times faster than what would be acceptable in order to assume a 30-year service life for CSP plants.

NREL researcher Judith Gomez-Vidal is looking to nickel coatings for a solution.

According to Gomez-Vidal in her paper, “Corrosion resistance of MCrAlX coatings in a molten chloride for thermal storage in concentrating solar power applications,” corrosion rates for these structures must be 20 micrometers per year or less. Using an atmospheric plasma spray NiCoCrAIY coating, Gomez-Vidal reports that she was able to reduce corrosion from more than 4,500 micrometers per year to just 190—short of the goal, but a vast improvement.

Good Progress, More Needed

“The use of surface protection is very promising to mitigate corrosion in molten salts in particular to those surfaces exposed to chlorine-containing vapor,” said Gomez-Vidal. However, “more R&D is needed to achieve the target corrosion level needed, which could include the synergy of combining surface protection with chemical control of the molten salt and the surrounding atmosphere.”

Gomez-Vidal is currently researching whether introducing oxygen might assist in the creation and repair of protective aluminum oxide scales in the coating.

The nickel coating research was funded by the DOE’s SunShot Initiative, an effort to drive down the cost of solar energy production and distribution in order to make the renewable energy source more practical for use by American homes and businesses.


Tagged categories: Coating Materials; Corrosion protection; Industrial coatings; NA; North America; Protective Coatings; Research and development; Salt exposure; Solar energy; U.S. Department of Energy

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