Mid-IR transmission window for corrosion detection beneath paint

The mid-infrared transmission window between 3.8–5.5 µm has been used to detect corrosion beneath a paint layer of 80–100 µm thickness using low power light emitted diodes. Two-dimensional images from a sample of painted metal with corrosion were obtained for 3.8 to 5.5 µm wavelengths. The best contrast for imaging corrosion is near 4.8 µm.