Protective Coatings

What are protective coatings? How are they different to paint and how do they work?

The terms paint and coating refer to different materials. Protective coatings are applied by painters, but they are very different from domestic paint and it is important to understand how they work so that they can be applied correctly. It is critical that painters follow manufacturer's directions meticulously and to specification because the products dry and cure in a different manner to domestic paints. This cannot be stressed enough.

Paint is primarily formulated for decorative purposes in private dwellings and commercial buildings. Coatings refer to materials designed for industrial use, protecting the asset against the environment and corrosion control.

Protective Coatings must:

  • Have good adhesion
  • Have excellent water and water vapour resistance:
  • Have good resistance to abrasion, impact and chemical attack.
  • Be capable of withstanding the particular environment for which they were chosen.

The characteristics of a coating are determined by the choice of resins, pigments, solvents and additives used. For example:

A primer coat:

  • Should have good adhesion to the substrate
  • Should be compatible with chosen intermediate or top coats
  • May need to provide corrosion resistance or protection for the substrate.

An intermediate or undercoat should:

  • Have good cohesion to the primer coat
  • Be compatible with the chosen top coat
  • Fill irregularities in the primer surface
  • Provide a resistance to water vapour
  • Act as a barrier to corrosive agents

A top coat should:

  • Have an excellent resistance to water vapour
  • Resist corrosive agents or chemicals in the environment
  • Have good adhesion to the intermediate coat
  • Be Ultra Violet light resistant
  • Be aesthetically pleasing

The most common products a painter will use are:

  • Epoxymastics, or 'Surface Tolerant Epoxies'
  • Two-pack Polyurethanes
  • Two-pack Water-based Epoxies
  • Micaceous Iron Oxide