PosiTest AT — Visual Analysis and Recording of Test Results

Illustration showing a dolly face and coated surface in a scenario with a 100% cohesive fracture, versus 100% adhesive fracture

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.

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  • 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 itself, the coating or dolly (no coating visible on the dolly face).
Image illustrating a crosscut of different fractures: Cohesive fracture (within a layer), Adhesive fracture (between layers), and Glue failure (coating/glue)

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.

Illustration depicts a cross section of dolly pull-off adhesion test sample with 5 layers of paint in addition to the substrate, dolly, and adhesive.

Examples

(based on above five layer illustration)

An illustration example of a 100% cohesive fracture with a screenshot from the PosiTest AT showing the same results
An illustration example of a 70% cohesive fracture with a screenshot from the PosiTest AT showing the same results