The standard 55-gallon barrel is frequently used for storage of hazardous chemicals and low-level radioactive materials. Corrosion on the inner surface of the barrels produced by the stored materials may produce wall thinning. Wall thinning may be a problem either in long-term storage or where the barrels must be moved. Ultrasonics could determine the degree this thinning, but the nature of the stored material may discourage the use of the couplant associated with ultrasonics. Electromagnetic fields suggest a way to detect wall thinning rapidly and without the use of couplant.