Surface Roughness Specifications for Sandblasting Before Thermal Spraying

       The surface roughness after sandblasting is based on the thermal spray surface preparation standard established by the National Society of Corrosion Engineers (NACE) Technical Committee T-60. The most suitable grade for sandblasting roughening of steel surfaces is NACE No.1. A grit blasted surface that meets NACE No. 1 standards, is a metal surface with an off-white homogeneous that has been roughened to "anchor" the coating, while being free of oil, grease, contamination, No rolling scale, no rust spots, no corrosion, no oxides, no paint and other foreign matter (comparable to SSPC-SP5-63 white metal substrate blast cleaning).



Generally, as the surface roughness Ra increases, the bonding strength also increases, but the degree of improving the bonding performance decreases after exceeding 10um.



For most spray coatings, when the surface roughness Ra is 2.5~13um, it can meet the spraying requirements; in some special cases, especially thin metal parts, a surface with a roughness Ra of 1.3um can be used; For some workpieces sprayed with low melting point materials and alloys (such as zinc), the surface roughness Ra should be at least 6um.