White metal blast cleaning is used when a totally cleaned surface is required. This method of cleaning is defined as a blast cleaned surface with a gray-white uniform metallic color. It shall be free of all oil, grease, dirt, mill scale, rust, corrosion products, oxides, paint, stains, streaks or any other contaminant across 100% of every square inch.
Near-white blast cleaning is defined as one from which all oil, grease, dirt, mill scale, rust, corrosion products, oxides, paint or any other contaminants have been completely removed from the surface. Very light shadows, very slight streaks or discolorations caused by rust stain, mill scale oxides or slight tight residues of paint or coating are permitted to remain.. Only 5% of every square inch may contain the slight discolorations mentioned above.
Commercial blast cleaned surface is defined as one in which all oil, grease, dirt, mill scale, rust and old paint have been completely removed from the blast cleaned surface, except that slight streaks, or discolorations caused by rust stain, mill scale oxides, or slight tightly adherent residues of paint of coating may remain. If the surface is pitted, slight residues of rust or paint may remain in the bottom of the pits. The slight discolorations mentioned above are limited to one-third of every square inch.
Brush-off blast is defined as one in which all oil, grease, dirt, rust scale, loose mill scale, loose rust and loose paint or coatings are completely removed. Tight mill scale and tighly adherent rust and paint or coatings may remain as long as the entire surface has been exposed to abrasive blasting.