Upon completion of a pull-off test, the dolly and coated surface should be examined. In addition to pull-off force, many National and International standards such as ASTM D4541 and ISO 4624 require the nature of the fracture to be recorded.
- Cohesive fracture: fracture occurs within a coating layer (same coating on dolly face and coated surface).
- Adhesive fracture: fracture occurs at the interface between layers (coating on dolly face differs from surface).
- Glue failure: visible separation of the glue from iteself, the coating or dolly (no coating visible on the dolly face).
The cohesive and adhesive fracture visual analysis can be recorded using the PosiTest AT-A's keypad or touch screen display. Alternatively, the information can be reported post test using the PosiTector App.
Fractures are visually estimated and recorded as a percent of each. The two layer example below illustrates a cohesive fracture within coating layer 1 and layer 2 (visually estimated at 50% each). Recorded results are included in reports.
(based on above five layer illustration)
100% cohesive fracture at D/E coating interface (layer 3/layer 4)
70% cohesive failure within layer 1; 30% cohesive within layer 2