An essential requirement of protective coatings is that they adhere to the substrate to which they are applied. Peel resistance test may be conducted either using a constant rate of peel or using a constant force, usually provided by a peeling apparatus for pipe or a hanging mass test set up. Peel adhesion testing by constant rate gives a quantitative value for peel force required to peel the sleeve. An important factor in this test is assessment of the mode of failure, which helps to determine the weakest adhesion point within the coating system.
The test starts with making two cuts 25 ± 1 mm apart through the coating to the steel substrate with the utility knife from the 90° position to the 180° position. The coating is cut at a right angle at the 90° position and peeled down to the 135° position. Appropriate mass is then attached to the free end of the peel strip and the mass is released and allowed to remove the peel strip. The peeling time is measured in minutes from the 135° position to the 180° position. The distance peeled in millimeters is measured from the time the test was initiated until it was terminated. Finally, the mode of failure is analyzed.