Zinc flake coat­ings

Zinc flake coatings consist of lamellar metal particles in an inorganic binder matrix, which are applied non-electrolytically.  They are applied to the component like a wet paint using various processes and cross-linked to a solid film by heat treatment at typically 180 - 240°C (solvent-dilutable) or 290 - 310°C (water-dilutable).

In addition to binders and solvents, the liquid coating material contains a very high proportion of corrosion protection pigments.  After application and during heating of the components, these zinc and aluminium (or alloy) plates align in many layers.  As the solvents evaporate during the heating process, many layers of these lamellas are formed which lie close to each other and are each coated with a binder.  This cross-links at higher temperatures and thus produces a coating that adheres to the substrate material.

An additionally applied topcoat favours further properties of the zinc flake system.  The sealing is often produced in the same application process and at similar temperatures as the basecoat. The process is aimed at the components to be coated and the requirements for the resulting coating.

The following control variables are relevant for the structure and quality of the coating in an adapted system technology:

• Surface quality of the components to be coated
• Viscosity and solids content of the coating material
• Application parameters (depending on process)
• Temperature and time of heat treatment for crosslinking/curing
• Racks / goods movement adapted to the component geometry

Mainly metallic components made of ferrous materials are coated in industrial plants.  Zinc flake systems are typically used in the automotive industry, but also in commercial vehicles, wind turbines, agricultural machines, buildings and especially on springs, clamps, screws and other connecting elements.

•  Immersion centrifugal process (bulk material in baskets)
• Submerged centrifugal rack process
• Spray application (on racks, individual parts or bulk material in rotating drums)
• Dip drawing