COLUMBUS, Ohio -- Researchers have developed a new corrosion-resistant diffusion coating for steam pipes used in power-plant boilers that will reduce maintenance costs for plants and could make electricity less expensive.

Robert Rapp, a professor of materials science and engineering at Ohio State University, has designed a chromium-silicon coating for steam pipes that makes them resistant to sulfur gases, fly ash and other impurities released during the burning of coal. These combustion products attack the pipes and can cause holes through the steel walls of the pipes.

Rapp's research was detailed in a recent issue of the journal Oxidation of Metals.

"When the coating is introduced to the market, power plants and other chemical plants, incinerators, etc. that use it can run their plants longer between scheduled repairs and may experience fewer unscheduled shutdowns," Rapp said. "That could allow the plants to make electricity more efficiently."

The coating would be applied to thousands of low-alloy steel pipes that line the walls of power plant boilers. The exterior

of the pipes are exposed to deposits released during the burning of coal. These agents, including fly ash, slag, oxidizing gases and condensated salts, produce a corrosive film on the pipes. Over time, the corrosion attacks the steel, causing water leaks.

"Power plant crews can clean up the tubes and knock off the condensates during operation, but once a hole passes, there's a water leak," Rapp said. "Too many water leaks lead to a plant shutdown."

An unplanned plant shutdown can cost millions of dollars in lost energy production and other costs, Rapp said. When a plant can't produce energy for its customers, the company must purchase energy from a competitor to supply customer needs.

Applying the coating to the pipes is not a complicated or costly process, Rapp said, although he could not provide cost figures for the procedure.

"It's a simple matter and one that's worth it, or plants wouldn't be interested in the technology," he said.

There are two methods for making the coating. Rapp and graduate student Mark Harper have received a patent on one method. The research team has applied for a patent on the second method, which uses similar materials, but could be more cost-efficient.

He has also conducted research on a coating comprised of chromium and aluminum, which would have similar applications as the chromium-silicon coating.

Rapp said it will be several years before the technology will be available for power plants.

His work has been sponsored by the U.S. Department of Energy and Babcock and Wilcox, a builder of power plants. Babcock and Wilcox has provided funding for the Ohio State patents on Rapp's technology. The company is working with Ohio State's Office of Technology Transfer to obtain first rights to the technology.

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Contact: Robert Rapp, (614) 292-6178

Written by Kelli Whitlock, (614) 292-9475