In order to perform in a satisfactory manner, coatings need to stick to the substrates on which they are applied. There are various recognised techniques that can be used for determining the strength of bonding of a coating to the substrate. Read and find out about some of the different types of coating adhesion tester methods.
#1. Knife Test
This is a basic coating adhesion tester method in which a utility knife is used for picking at the coating. Generally, it can be established whether the adhesion of a coating to another coating or a substrate is enough. The performance is based on the size of the coating that is removed as well as how difficult it is to remove the coating from substrate.
Generally, with the help of a cutting guide and in knife an X-cut is created through the coating all the way down to the substrate. The knife point is used at the vertex in order to try and elevate the coating from the coating beneath or the substrate below.
This kind of coating adhesion tester method is very subjective, and its value is based on the experience of the inspector. A coating with significant cohesive strength might seem to have worse adhesion as compared to a brittle one and thus – easily fractures when probed. Standard Test Method for Evaluating Adhesion by Knife is a standard technique for applying and performing this kind of test.
#2. Tape Test
This is a more formal kind of knife test on metal substrates. There is application and removal of pressure-sensitive tapes from cuts that are created in the coating. This kind of test has two variants – the cross-hatch tape test and the X-cut tape test.
The latter is intended mainly for use at job sites. An X-cut is created all the way down to the substrate through the coating with the help of a cutting device like:
- Knife,
- Scalpel or
- Sharp razor blade
In order to make straight cuts a straight hard metal edge or steel is used.
The tip is put on the middle area of the intersection of the cuts and rapidly removed then. Then the X cut section is inspected for coating removal from the underlying coating or substrate, as well as from associated surfaces.
standard coating adhesion tester method for evaluating adhesion by knife is a standard method for applying and performing this kind of test.
#3. Pull-Off Adhesion Test
This is a more quantitative adhesion test in which a loading fixture, which is commonly referred to as stub or dolly, is affixed to a coating with the help of an adhesive. With the help of a portable pull off coating adhesion tester method, there is an increasing application of a load until the dolly gets pulled off.
This method of testing maximizes tensile stress then the shear stress that is applied by various other techniques like knife adhesion or scrape adhesion and the results might not be comparable in nature. The pull of strength measurements also depends on the kind of apparatus that is used in this kind of testing. Results for same kinds of coatings on substrates or results obtained with the help of various devices with different types of stiffness might not be comparable in nature.
#4. Scrape Test
Generally, it is carried out in a lab setting and limited to conducting tests on flat panel smooth surfaces. The level of addition is determined with the help of a specific type of apparatus known as balanced-beam scrape-adhesion tester.
Standard coating adhesion tester method of Organic Coatings by Scrape Adhesion is a standard technique that is used in order to apply and perform this kind of test, which has extreme usefulness.