Adherence* failure and measurement: some troubling questions

It is pointed out that many methods used to determine the adherence of films and coatings to their substrates are inadequate. Sometimes, they are misleading. Key test conditions must appropriately simulate the conditions of service under which adherence failure may be brought about. It is indicated that the test environment and the rate and mode of stress application are among the important factors to consider. The nature of adherence failure is discussed against a background of multibarrier fracture kinetics. A brief review of multibarrier fracture kinetics as it applies to adherence failure and testing is given. Some evidence is cited to show that competitive failure mechanisms operate in many cases of adherence failure, and that which mechanism dominates depends on the conditions of failure.