Why prepare the surface before coating?

Surface preparation is the most important step in any painting or anticorrosive coating system. Regardless of the quality of the paint used, if the surface is not correctly prepared, the coating will fail prematurely — with the cost that implies in materials, labor and downtime.

The objective of surface preparation by shot blasting is twofold. First, to remove all contaminants that prevent coating adhesion: rust, mill scale, foundry sand, old paint, grease and salts. Second, to generate a controlled roughness profile — the anchor profile — that maximizes the contact surface between the coating and the substrate, multiplying mechanical adhesion.

International standards ISO 8501 (Europe) and SSPC (North America) define the cleanliness grades required for each type of coating and exposure condition. Grade Sa 2½ (ISO 8501) is the most frequently required in industrial paint specifications: surface free of mill scale, rust and contaminants, with light shadows permitted. Grade Sa 3 is the most demanding: bright metal surface free of any visible contaminant.

Automatic turbine shot blasting is the most efficient method for surface preparation in production lines: high productivity, uniform and reproducible anchor profile, and a process verifiable with a profilometer. For field work or large parts, portable compressed air blast machines are used.