Grit blast is the best way to prepare a surface for thermal spray.  This is after all oil and grease has been  removed from the part to be sprayed. The purpose of grit blasting is to remove all oxides and foreign material from the surface being sprayed. More importantly, the grit blast operation results in a surface that has many pits and textured areas where the thermal spray can attache to and lock into.  The most common material used for grit blast is aluminum oxide and chilled iron.

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Surface Preparation for Thermal Spray