Near white metal blast cleaning is a set standard procedure defined by SSPC – SP 10/NACE No. 2 for cleaning metal surfaces with abrasives to prepare the surface for corrosion proofing by the application of paints and coatings.
A near white metal blast cleaning differs from white metal blast cleaning since the surface is not completely cleaned. The surface may contain some staining, but not more than 5% of each unit area of surface.
When viewed without a magnifying glass, near white metal blast cleaned surfaces shall be free from all visible oils, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products and other foreign matter, except for staining. Per the SSPC – SP 10/NACE No. 2 standard, the staining should not be more than 5% of each unit area of surface.
Stains may be from rust, mill scale or previously applied coatings. The surface’s appearance after a near white metal blast cleaning process is generally slightly discolored, consisting of slight streaks or light shadows from previous coatings.