Adhesive failure
Adhesive failure turns up in 3 fields: thermal spray, adhesives, waterproofing. Here is what it means to the people in each one.
Adhesive failure in thermal spray
A bond test break at the coating-substrate interface, meaning the coating let go of the base metal.
Failure mode in which the coating separates cleanly from the substrate, leaving bare, blasted metal on the test button. It points to problems at the bond line: contamination, low profile, flash rust, oxidized bond coat or excessive stress. Specs often require not only a minimum strength but also that failures are not adhesive.
"Adhesive failure on all three buttons, bare grit-blasted metal, go look at the blast cabinet."
Adhesive failure in adhesives
A break at the interface between adhesive and part, leaving one surface clean or nearly clean.
Interfacial failure means the adhesive never bonded well to that surface. Common causes are oil, mold release, oxide, plasticizers, blush, low surface energy, missed primer or exceeded open time. Because the adhesive itself was stronger than its grip, the fix lies in surface preparation or adhesive selection, not in more adhesive. A shiny, bare surface with a clean print of the bead is the classic sign.
"Bead peeled off the panel in one piece, clean metal underneath, that's adhesive failure. Who skipped the wipe?"
Adhesive failure in waterproofing
A sealant pulling cleanly away from one joint face, leaving the substrate bare.
Adhesive loss usually comes from dirty or wet surfaces, laitance, old sealant residue, form release, missing or wrong primer, water repellent applied before sealing, or tooling that never pushed the sealant against the face. In the field it shows as a gap along one side of the joint. Pull tests and adhesion mock-ups catch it before a whole facade is sealed.
"Sealant's let go of the precast on every joint, adhesive failure, I bet they never primed."