Even a careful eye and conventional technology can't spot one of the most insidious effects of age and weather on aircraft--the corrosion of aluminum joints deep below the surface.
But now a new magnetism-based technique has proven itself able to locate that hidden damage, report physicist John Wikswo and engineer Grant Skennerton of Vanderbilt University in Nashville. The technique has already produced a surprise: Salt solutions of increasing concentration don't cause increasing amounts of corrosion at subsurface joints, as they do on airplane surfaces. The researchers say this suggests that different corrosion chemistries are at work.
The technique works because magnetic fields associated with a piece of metal change in strength as corrosion worsens. Taking advantage of this trait, Wikswo and Skennerton analyzed retired aluminum aircraft parts with a sensitive instrument known as a Superconducting Quantum Interference Device, or SQUID, which can sense subtle magnetic