In the Pull-Off Test the load is applied perpendicularly to the coating surface similar to the tensile test used for measuring tensile strength of materials.
The loading fixture (dolly, stub) is attached to the coating by an adhesive.
The load applied to the dolly is increased gradually until the coating is separated (peeled off) from the substrate.
The test may be terminated at a specific value of load if this value is set as the required minimum level of the adhesion strength.
I the Pull-Off Test the tensile strength of the coating bonding is measured therefore its results are not directly comparable with other test methods where the shear stress is applied.
Another limitation of the Pull-Off Tests is the strength of the adhesive bonding between the dolly and the coating surface. The failure occurs along this surface if it is weaker than the adhesion of the coating to the substrate.