Award for Smart, High-Performance Coating

23 August 2002

The U.S. Department of Energy's Brookhaven National Laboratory and National Renewable Energy Laboratory (NREL), along with industrial partners Bob Curran & Sons and Ticona Corporation, have won a 2002 R&D 100 Award for developing a smart, high-performance coating.

This polyphenylenesulfide (PPS) coating system is particularly suited for use in carbon-steel heat exchanger tubes in geothermal power plants.

R&D 100 Awards are given annually by R&D Magazine to the top 100 technological achievements of the year. Typically, these are innovations that transform basic science into useful products. The awards will be presented in Chicago on October 16.

Geothermal fluid from the earth's core is pumped through hundreds of carbon-steel heat-exchanger tubes in geothermal power plants, where the fluid is used for driving electricity-generating turbines. The hot, wet environment can corrode, oxidize and foul carbon-steel heat-exchanger tubes. Also, mineral deposits reduce heat transfer through the tube walls.

The PPS coating system, which has been commercialized under the trade name CurraLon (trademark), effectively deals with these problems. In fact, the PPS coating system shows dramatic improvements in bonding durability, resistance to wear and abrasion, and service lifetime and cost, compared to competitive coatings.

Toshifumi Sugama, the Brookhaven Lab chemist who developed the coating and winner of four R&D 100 Awards, said, ""In developing this new system, my colleagues and I have taken a giant leap forward in the technology of coating steel surfaces for use in hostile, corrosive environments. We estimate that the PPS coating system will have a useful life of 20 years in geothermal environments before service is needed. Other coating systems that we tested needed service after six months or less.""

The PPS coating system is applied to heat-exchanger tubes in three layers. The first layer is a zinc phosphate ceramic primer, which strongly binds to the steel and prevents corrosion. The second layer, a tough, anti-corrosive carbon-fiber/PPS matrix, dramatically enhances heat conductivity. The final layer, a calcium bialuminate (CBA)-filled PPS/Teflon-blend alloy, makes the coating system ""smart"" by giving it self-healing properties. The CBA filler repairs damage to the PPS/Teflon matrix by filling in micro- and nano-sized cracks generated by physical wear and impacts. Nano refers to cracks the size of one-billionth of a meter, while micro cracks, still tiny, are a thousand times larger.

While the PPS coating system is currently being used in geothermal power plants around the world, it also has other potential applications. Any facility with a harsh, hot, corrosive environment, such as chemical, power generation, seawater desalination, water treatment, and air-conditioning facilities, may benefit from use of the coating, which can be used on a range of components.

Brookhaven and NREL researchers developed the coating system under the U.S. Department of Energy's Geothermal Materials Program, and the technology was transferred to Bob Curran & Sons, Dickenson, Texas. Ticona Corporation of Summit, New Jersey, manufactures the PPS used in the coating.

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