Surface preparation grade

Surface preparation in which abrasive particles such as grit, shot or garnet are propelled at high velocity against a surface using compressed air or centrifugal wheels, removing rust, mill scale and old coatings while creating a surface profile. The achieved cleanliness is assessed against standardised preparation grades.

The peak to valley roughness imparted to a substrate by abrasive blast cleaning, which provides a mechanical key for coating adhesion. The profile must be matched to the coating system and is measured using comparators, replica tape or stylus instruments.

A preparatory coating applied to a substrate before an adhesive, sealant, coating or waterproofing membrane, improving adhesion by sealing porosity, binding dust or providing a chemically compatible surface. Primer selection depends on both the substrate and the product to be applied over it.