Patent ID: 8372216

Claim:
A method for continuous surface treatment of a metal strip with a liquid formulation (F), in which a metal strip is moved longitudinally through an apparatus for surface treatment of metal strips that comprises at least one device for applying the formulation (F) and in which the formulation (F) is applied to the metal strip by means of the device, the amount of formulation to be applied being calculated so as to form a nonmetallic finish coat having a coat thickness of less than 3 μm on the metal surface, which method comprises equipping the apparatus employed, downstream of the device—as viewed in the running direction of the strip—with at least one IR sensor which faces a coated side of the strip, operates in reflection geometry, and comprises at least one broadband-emitting IR source, and also at least one IR multichannel detector comprising at least two measurement channels, each of the measurement channels being equipped with an IR filter which is mounted upstream of the measurement channel in question, and each of which is transmissive only for a particular wavelength range of the IR radiation with the proviso that at least two different IR filters are used, and in which the IR source emits IR radiation toward the coated strip surface, the radiation is partly reflected from the strip surface, and the intensity of the reflected radiation is measured with the IR multichannel detector, and from the intensity measurement, by means of an arithmetic unit, the coat thickness of the finish coat is calculated.