What grit sandpaper should be used for initial surface prep?

• A. 60 grit
• B. 100 grit
• C. 80 grit
• D. 120 grit

Answer: (C)

The main idea is to create a surface texture that lets coatings grip well while removing the stuff that can interfere with adhesion. For initial surface prep, you want a mid-range grit. It’s abrasive enough to remove loose paint, rust, and scale and to form good anchor points for the coating, but it’s not so aggressive that it will gouge the substrate or create deep scratches that require extra repair. Using a too-coarse grit can damage the metal, while using a too-fine grit won't remove the old coating or corrosion effectively. After this first roughing pass, you’d switch to progressively finer grits to smooth the surface before applying primer.