Detection system and method of detecting corrosion under an outer protective layer

Abstract

Wide-angled incoherent millimeter or sub-millimeter electromagnetic waves from an extended active source are used to probe substrates and their protective coatings or outer layers, such as paint or thermal insulation. The incoherent waves provide dispersion and angular variation with respect to angular incidence to the substrate. Illumination of the substrate permits differentiation between un-corroded and corroded sections of the sample because reflectivity, emissivity and/or transmissivity from the substrate or protective coating various according to its homogeneousness. A detector/camera is arranged to identify and resolve differences in detected power within an observed frequency range of the area under test, with this contrast in power being relative to either adjacent areas or anticipated reference levels. The power differences therefore signify the presence or lack of corrosion or, indeed, the presence of anomalies within or on the substrate or in or under the protective coating or layer applied to the substrate.