Ceramic Coatings May Protect Jet Engines From Volcanic Ash

Last year's $2 billion shutdown of European airspace following a volcanic eruption in Iceland alerted everyone to the danger that ash clouds can pose to aircraft engines. Now, researchers have discovered that a new class of ceramic coatings could offer jet engines special protection against volcanic ash damage in the future.

For a study published online in the Early View edition of the journal Advanced Materials, the researchers tested two coatings that were originally developed to keep airborne sand from damaging jet engines, and found that the coatings also resist damage caused by ash deposits.

"Of course, it's best for jets to avoid ash in the first place," said Nitin Padture, College of Engineering Distinguished Professor at the Ohio State University, who led the study. "That's not always possible. We determined that these coatings could offer sufficient protection against small amounts of ash ingested by the engine over time."

However, large amounts of ash can temporarily jam a jet engine and cause it to stall, he explained. These coatings would not be useful in those extreme circumstances.

Temperatures inside an engine reach up to 2,500 degrees Fahrenheit, and ceramic thermal-barrier coatings insulate metallic engine parts from that heat. The ingested ash melts onto the coating and penetrates the coating. Upon cooling, the molten ash forms a brittle glass that flakes off, taking the coating with it.

It's a familiar story to Padture, who previously invented a new coating composition to prevent similar engine damage caused by sand.

Like sand, ash is made mostly of silica. When the Icelandic volcano Eyjafjallajökull erupted in April 2010, it billowed clouds of silicate ash.

"Ash poses a threat very similar to sand, but ash composition varies widely depending on the type of volcano. After what happened in Iceland, we wanted to see how ash interacted with our new thermal barrier coating, and whether the underlying damage mechanisms were any different," he said.