Paint changes color as corrosion warning.

An early warning system for aircraft degradation--a paint that changes color when the metal beneath it begins to corrode--is being developed by Gerald Frankel, associate professor of materials science and engineering, and graduate student Jian Zhang, Ohio State University, Columbus. While maintenance crews can search for corrosion with several high-tech tools including electromagnetic currents and ultrasound, the paint is potentially both less expensive and more sensitive because it makes tiny pockets of corrosion visible to the naked eye, revealing cavities as shallow as 15 micrometers--about one-fifth the width of a human hair.

"We would like to know early where corrosion is occurring on airplanes, but it starts in hidden crevices, so it's hard to find," Frankel points out. "One solution is to implant corrosion sensors in an airplane, but sensors only detect corrosion in their immediate area, and there are lots of potential spots for corrosion on an airplane. That led us to this notion of modifying paint, because on an airplane paint is everywhere."

He cautions, though, that the paint would not be ready for actual use on airplanes for a number of years. He did say, however, that with further development, the paint could save military and commercial maintenance crews from having to tear aircraft apart to check for corrosion.

The chemical reaction that occurs during corrosion often increases the pH of the region where it takes place. The researchers mixed clear paint with laboratory chemicals...