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Measurements Through Coatings

Paint, epoxy, and similar protective coatings on steel frequently present a potential issue in corrosion survey applications. Because the sound velocity of nonmetallic coatings is usually about half that of steel, a coating can add an error of double its actual thickness to a measurement. In many such cases, echo-to-echo measurement can be utilized to measure the thickness of the metal only, since multiple backwall echoes exist in metal but not commonly in coatings. Additionally, some advanced instruments use sophisticated signal processing techniques to electronically subtract coating thickness from the measured reading.

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