CCCs are frequently applied to steel coil and aluminium coil surfaces to render them corrosive resistant and to establish an adhesive base for organic coatings. Chromium VI, hexavalent chromium has been the most predominantly used form, but it’s usage is being curtailed through RoSH legislation owing to it’s toxicity. Chromium III is safe to use, and is still being used by many aluminium manufacturers in addition to newer alternatives based upon phosphates, manganates, silanes, etc
As NIR measurement is non contact and non destructive, the MCT 360 can be simply installed on line after the coating has been applied to measure the coat weight on a continuous basis, enabling automatic or manual adjustment to the coater. Control of coat weight is important as it impacts the physical and chemical properties of the sheet metal. The CCCs also “tie” the paint to the metal substrate to reduce or eliminate paint peel issues. This measurement is similar to other converting applications.
The gauge is installed parallel to and at a distance of 150 – 300mm from the metal sheet as it passes over a large diameter steel roller, or approaches rollers (for minimal web flutter). Measurement is made on the wet coat weight but the read-out is in terms of dry coat weight. The solids ratio must be kept constant or be known, so that a correction factor can be applied to the measurement read-out.
|Dry coatweight range||Expected measurement accuracy|
|*3-8 mg m-2||+/- 0.05 mg m-2|
* Note other coat weight ranges can be measured.