Manufacturing Process of Color Coated Aluminum Coil Sheet

To coat aluminum coil is to improve its adaptability to severe environments by giving it a proper surface protective treatment. Manufacturing process of color coated aluminum coil sheet includes raw material feeding, pre-treatment, coating, paint solidification and coated coil rolling.

1. Raw material feeding

The continuous unwinding of the unwinder ensures the continuous and stable input line of the aluminum coil. Some suppliers adopt the cross-rotating beam type winder, and others adopt the double-stage alternate undulating machine, both aimed to timely supply the roll.

2. Pre-treatment, including surface cleaning and chemical treatment. The water spray method is repeated to make the surface of the aluminum coil clean. This method is more efficient than traditional methods, and water can be reused as well. Chemical treatment is to ensure that the subsequent paint will adhere firmly to the aluminum coil. At this stage, the conversion film is chemically formed on the aluminum surface. Effective process technology helps to improve product quality and reduce waste of resources.

3. Coil coating

The color coated aluminum coil coating process is mainly divided into two stages: primer coating and top coating. There are at least two roll coaters in one production line to ensure two coats of topcoat and primer. In the first stage, the aluminum coil passes through a roll coater and is coated on one or both sides with a primer. Dried aluminum coil goes through two roll coaters, at which time the aluminum roll is coated on one or both sides.

There are four coating methods. 1. Brushing. It allows the coating to penetrate into the pores of the metal surface and enhances the adhesion of the metal; 2. Scrape coating. Here coatings of high liquid purity and high viscosity are adopted; 3. Dip coating. As a traditional method, it is more likely to cause air pollution. 4. Electrostatic spraying. This method boasts less environmental pollution, high utilization rate of coating, good quality of coating and high efficiency.

4. The solidifying of the paint layer means that the aluminum coil roll that has just been painted should be fixed before the next roll surface to avoid adhesion and damage. Generally speaking, at least two curing boxes are needed. The coated aluminum coil goes through a curing oven in which the temperature is set at a stable value to ensure that the volatiles on the ribbon are removed and the coating is fully cured. According to the needs of the coating system, the curing temperature is set between 200 and 300 degrees Celsius, which is the key technical point to ensure product quality. In addition, in order to protect the environment and control costs, the mist of the solvent is evaporated by high temperature to heat the curing oven.

5. The step of rolling color coated aluminum coil ensures that the line speed is synchronized with the finished product transfer.

Sometimes there are subsequent processing steps. The color coated aluminum coil can be further slit or compressed to become shutters, coated aluminium sheets, embossed color coated aluminum sheets, coated aluminum strips etc.