Color Coated GL Steel Coils

Reverse Roll Coater Application
Precision paint application is achieved via reverse roll coaters, where engraved applicator rolls (60-200 lines/cm) meter coating thickness before transferring paint to the steel strip via precision-gapped backing rolls. Viscosity-controlled paints (80-300 cP) are pumped into enclosed chambers, eliminating solvent evaporation and ensuring 99.8% transfer efficiency. Coating weights are maintained within ±0.5g/m² by laser gauges feeding back to servo-controlled doctor blades. For dual-coat systems, the coater applies 5-8µm primer at 80-120 m/min, followed by IR flash-off and 15-25µm topcoat application – all within a single pass through the coating tower. Roll engraving geometry (trilobe, quadrangular) determines film build and appearance, with 140° line angles optimizing flow for architectural smoothness.

This technology enables unprecedented quality control. Reverse rotation minimizes shear forces, preventing pigment flocculation and achieving 60° gloss uniformity of ±2 GU across the coil. On-the-fly viscosity adjustment (±1 cP) compensates for solvent loss, maintaining film leveling for orange peel values <10 (ASTM D5767). For specialty finishes, coater heads can switch between solid colors and embossing basecoats within 30 seconds. The enclosed system reduces VOC emissions to <20g/m², complying with EU Industrial Emissions Directive. Critical performance metrics include: dry film thickness (DFT) variation <±0.3µm per NIST traceable sensors, cross-direction uniformity of ±0.1g/m², and defect densities <0.1 pinholes/m². Such precision allows PVDF topcoats to achieve 30-year fade warranties (ΔE<5 per AAMA 2605).