Roughness created by blasting, which gives molten splats peaks and undercuts to freeze around. It is measured with a stylus profilometer as Ra or Rz, or with replica tape on field steel. Many thermal spray specs call for roughly 2.5 to 10 micrometers Ra, while TSA on structural steel calls for a sharp, angular peak-to-valley profile of at least 2.5 mils (about 64 micrometers). Too little profile gives weak bond strength.
Profilometer reads 2 micron Ra on the shaft, that's light for the carbide, hit it again with fresh grit.
Check profile on the actual part or on a coupon of the same alloy and hardness; soft metal blasts to a different profile than a hard scrap plate.
Also heard as
- surface profile
- blast profile
- anchor pattern
- profile
Related terms
Grit blasting
Blasting a surface with angular abrasive to clean it and roughen it so the coating can grip.
Tooth
Shop word for the bite or roughness left on a blasted surface, the grip a coating needs to hold on.
Bond strength
How hard you must pull to tear a coating off its substrate, measured by gluing and tensile testing.
White metal
The highest blast-cleaning grade for steel: every trace of rust, scale and old coating removed.