Type of Multiple Coats:

1. Multiple coats from one type

• Barrier coat
• Same coating type (same generic type) applied in contrasting colours
• Self priming – Used as a primer and topcoat

2.Multiple coats from multiple types

         These are the most commonly used coating systems and generally include:

Primers

• Offer excellent adhesion to the substrate.
• Provide a base or key for subsequent application of coats
• Protection of the substrate either as inhibitor or barrier, or being sacrificial can contain both of the above characteristics or a combination thereof.

Three types of primers

• Galvanic / Sacrificial
• Inhibitive
• Barrier (non inhibitive)

Sealers

When surfaces are porous, absorption of the paint medium can upset the pigment/blinder ratio, of the applied product. Sealers are therefore used to eliminate the suction. In some cases the formulation of the primer can be modified to enable it to function as a sealer. Hence, they are sometimes referred to as Primer Sealer.

Intermediate Coats

Act as a barrier and a base for the finish coat. In a three coat system it must act as a tie between the primer and finish coat, and may be used to build higher dry film thickness. Intermediate coats usually dry to an eggshell finish, which provide suitable good adhesion for the finishing coat.

Finish Coats

Act as a final coat for the full paint system. They reduce the rate of moisture permeation to the underlying coatings. They also confer reflectivity, reduce photo degradation or affects color coding. On drying they exhibit a high gloss, semi gloss, eggshell or matt finish.