What Does Adhesion Test Failure Mean?
An adhesion test failure refers to the failure of a coating to adhere to a substrate when its adhesive strength is tested according to the ASTM D 4541 standard specifications.
Industrial paints and coatings are tested for their adhesive strength and properties with the help of a pull-off type instrument, which consists of a pull stub that is bonded to the coating's surface. Once the coating dries and the bond is strong, a tensile force is applied by the pull stub and increased until the coating detaches. This force is recorded by the pull stub and checked to see if it is within the permissible limits of adhesive strength. If the coating detaches before the permissible limits of force, it is said to have undergone an adhesion test failure.
Corrosionpedia Explains Adhesion Test Failure
A strong adhesion of a coating or paint depends on various factors such as:
- Physical properties of the substrate and the coating
- Surface geometry where the coating has been applied
- Test parameters, conditions and type of instrument used to check the adhesive strength
- Test method
- Skills of the operator
- Consistency and rate at which the tensile force or load is applied
If any of the factors are insufficient the chances of an adhesion test failure increases. To test the adhesive strength, a perpendicular tensile load is applied and the amount of tensile force or load at which the coating breaks from the substrate (i.e., at which the coating detaches) is recorded. The test is performed by securing loading fixtures (dollies) perpendicular to the surface of a coating with an adhesive. The tensile force is gradually increased and deformations in the coating surface are inspected. The force is increased until a complete deformation of the coating occurs, which breaks the bond between the coating and the substrate.
Industrial coatings and paint manufacturers provide a descriptive manual about the adhesive strength of their coatings.