In the paint

Paint

Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

 and coating

Coating

Coating is a covering that is applied to the surface of an object, usually referred to as the substrate. In many cases coatings are applied to improve surface properties of the substrate, such as appearance, adhesion, wetability, corrosion resistance, wear resistance, and scratch resistance...

 industries, paint adhesion testing is necessary to determine if the paint or coating will adhere properly to the substrates

Substrate (building)

The word substrate comes from the Latin sub - stratum meaning 'the level below' and refers to any material existing or extracted from beneath the topsoil, including sand, chalk and clay....

 to which they are applied. There are three different tests to measure the resistance of paints and coatings from substrates: cross-cut test, scrape adhesion, and pull-off test.

Cross-Cut Test

A right angle lattice

Latticework

Latticework is a framework consisting of a criss-crossed pattern of strips of building material, typically wood or metal. The design is created by crossing the strips to form a network...

 pattern is used to measure the resistance of paints and coatings to separation from substrates. The pattern is cut into the coating and penetrates through the substrate. An uncalibrated pressure sensitive tape

Pressure sensitive tape

Pressure-sensitive tape, known also in various countries as PSA tape, adhesive tape, self-stick tape, sticky tape, or just tape, is an adhesive tape that will stick with application pressure, without the need for solvent, heat, or water for activation...

 is applied to the sample and pulled off. This testing method is usually used for a fast pass or fail test. If this test is used on a multi-coated sample, assessment of the resistance to separation of individual layers of the coating from each other can be made.

Scrape Adhesion

The scrape adhesion test measures the determination of the adhesion of organic coatings when applied to smooth, flat panel surfaces. It is helpful in giving relative ratings for a number of coated panels showing significant differences in adhesion. The materials being tested are applied at uniform thickness to flat panels, mainly some sort of sheet metal. When the materials have dried the adhesion is determined by pressing panels under a rounded stylus that is loaded with increasing amounts of weight until the coating is removed from the substrate surface.

Pull-Off Test

The adhesion of a coating or several coated sample of any paint product is measured by assessing the minimum tensile stress needed to detach or rupture the coating perpendicular to the substrate. Unlike the other methods, this method maximizes the tensile stress, therefore results may not be comparable to the others. The test is done by securing a dolly perpendicular to the surface of a coating with an adhesive. Then the testing apparatus is attached to the loading fixture and is then aligned to apply tension perpendicular to the test surface. The force that is applied gradually increases and is monitored until a plug of coating is detached, or a previously specified value is reached.