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20 April 1995 Detection of aluminum corrosion by evanescent wave absorption spectroscopy with optical fibers
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Remote detection of natural corrosion of aluminum alloy has been demonstrated using optical fiber Fourier transform infrared evanescent wave absorption spectroscopy. This technique is a particular example of Attenuated Total Reflectance (ATR) spectroscopy. Significant absorption features in the spectral range from 3300 to 3700 wavenumbers have been recorded. For comparison, spectra of the same corrosion samples of aluminum have also been collected using a zinc selenide crystal as the ATR element. Both optical fiber and crystal ATR evanescent wave absorption spectra of pure aluminum hydroxide were recorded for reference. Formation of aluminum hydroxide is a major product of corrosion in aluminum and aluminum alloys. A four wavenumber resolution Michelson interferometer spectrometer was combined with a seven bounce zinc selenide crystal to make the ATR spectral reference measurements. The same interferometer spectrometer was used with 200 micrometer core diameter multimode chalcogenide optical fibers to make the evanescent wave absorption measurements simulating the remote detection process. The data was collected with one or two meter lengths of 500 micrometer diameter fibers which were decoated for 20 cm of their length. The optical fiber absorption measurements are very sensitive and can detect a very small amount of material which is in contact with the decoated fiber core. The qualitative results reported here demonstrate that the technique of optical fiber evanescent wave absorption spectroscopy may be used to monitor industrial corrosion of aluminum alloys and that quantitative analyses of this type of spectral data are possible.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Juock S. Namkung, Michael L. Hoke, Robert S. Rogowski, and Sacharia Albin "Detection of aluminum corrosion by evanescent wave absorption spectroscopy with optical fibers", Proc. SPIE 2444, Smart Structures and Materials 1995: Smart Sensing, Processing, and Instrumentation, (20 April 1995);

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