Already a method used in myriad applications, coil coating is now being used to apply coatings that help capture the power of the sun. The paint application method is being used to apply selective absorber coatings to aluminum strip for thermal energy applications at solar power plants. The process provides the precise layers of coatings needed for high performing solar absorber coatings.

According to Cleveland-based National Coil Coating Association, the coil coating process is well suited for specialty coatings used for solar energy because of the optimal surface preparation, coating adhesion and continuous control that are inherent to this process.

By using the coil coating process, thin coatings can be applied uniformly to metal strip, so a highly selective coating and several functional coats can be applied in precise, thin layers. The functional coats often include functional particles such as nanoparticles, metal particles, metallic oxide particles and pigments. Each coat has a job. For example, one layer may absorb short-wave solar radiation while also being transparent for long-wave radiant heat. The result is conduction of short-wave solar radiation converted into long-wave radiant heat, so the absorber plate is heated up as needed. Outside coats can be reflective for radiant heat so the absorbent coat emits little radiant heat to the outside. Additional coating layers provide humidity and temperature resistance to protect against corrosion. Other layers provide adhesion promoter properties that improve the endurance of the coating in the intense sun.

With the coil coating process, the coating thickness can be adjusted precisely by means of the gravure on the roller coaters and relative speed of line coil coating line. After coating, it is also possible to apply embossing to the painted metal in order to increase the absorbent surface without tears developing in the coating.

Coil coating is a continuous, highly automated process for coating metal before fabrication. In one continuous process, a coil of metal up to 72" wide moving up to 700 ft/min, is unwound, cleaned on both the top and bottom, chemically treated, primed, oven cured, top coated, oven cured again, rewound and prepared for shipment.