Anchor profile
Anchor profile turns up in 3 fields: corrosion, thermal spray, powder coating. Here is what it means to the people in each one.
Anchor profile in corrosion
Peak-to-valley roughness that blasting cuts into steel so a coating can grip, given in mils or microns.
The texture of peaks and valleys created by abrasive blasting, reported as average peak-to-valley height. Most coating systems call for roughly 1.5 to 4 mils (38 to 100 microns), with thick linings and thermal spray needing more. Inspectors measure it with replica tape and a spring micrometer, a depth micrometer or a stylus instrument. Too shallow and adhesion suffers; too deep and peaks poke through thin primers and rust.
"Replica tape reads 1.2 mils on the anchor profile, spec wants 2 to 3, switch to a coarser grit."
Anchor profile in thermal spray
The peak-and-valley roughness grit blasting leaves on a surface, which the coating locks onto.
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."
Anchor profile in powder coating
The peak-to-valley roughness that blasting cuts into steel, giving the coating something to grip.
Profile is measured in mils with replica tape or a profile depth gauge, and blasted steel for powder typically sits around 1.5 to 3 mils. Coarser media digs deeper. Too little profile weakens adhesion on heavy steel; too much leaves peaks that poke through a thin film and rust first. A common rule keeps total film build at least two to three times the profile depth.
"Anchor profile is reading near 4 on the grit, at 3 mils of powder those peaks are going to show."