Tensile adhesion measured with the ASTM C633 test: the coating is sprayed on the face of a 25 mm diameter cylinder, glued to a matching cylinder with high-strength epoxy, and pulled apart in a tensile machine. The result in MPa or psi is reported with the failure location. Plasma ceramics often reach 20 to 40 MPa, while HVOF carbides frequently exceed the strength of the glue at around 70 MPa.
Bond strength came in at 9,200 psi average, all cohesive in the top coat, so the bond line is fine.
Pull a few glue-only blanks with each batch of epoxy; if the glue alone pulls low, every coating result that day is suspect.
Also heard as
- adhesion strength
- tensile bond
- bond test
- C633 test
Related terms
Adhesive failure
A bond test break at the coating-substrate interface, meaning the coating let go of the base metal.
Cohesive failure
A bond test break inside the coating, with coating left on both halves of the test specimen.
Glue failure
Lab slang for a bond test where the epoxy broke first, so the coating is at least as strong as the glue.
Coupon
A small test piece sprayed alongside production parts to stand in for them in destructive tests.
Anchor profile
The peak-and-valley roughness grit blasting leaves on a surface, which the coating locks onto.