Enhancing Productivity in Coil Coatings

By Carlo Testa

Coil coatings must exhibit excellent application characteristics to ensure uniform appearance and defect-free films on production lines, often at speeds greater than 200 m/min. During a short curing sched­ule at high temperature, the paint must be formulated so that solvents are released at the correct rate and the chemical reactions formed should ensure enough flexi­bility to enable the coated metal to be bent without cracking or loss of adhesion of the paint film.

Each type of coating has its own specific advantages, be it thickness, gloss, hardness, flexibility, durability in extreme weather, or resistance to chemical attack. The choice of the most suitable system must be based on its usage and expected performance, and should always be agreed upon between the manufacturer and the client. Some coatings are applied in a single layer, to ei­ther one or both sides, while others are used with a primer in multi-layered systems.

There are two types of paint used for coil, based on either thermosetting or thermoplastic resins. The resins can be subdivided into eight general categories: alkyds, acrylics, epoxies, poly­esters, polyurethane, silicone-modified resins, polyvinyl chlorides (PVC), and polyvinyl fluorides (PVDF).