Paint Adhesion Testers
In order to perform satisfactorily, coatings must adhere to the substrates on which they are applied. There are three different adhesion test procedures to assess the resistance of paints to separate from the substrate. The cross cut test, also described as cross-hatch, uses a blade to cut through the coating to the substrate. At least two cuts are made that intersect at 90 degrees to get a right angle lattice pattern. The cross-cut area is observed for any adhesion failure. The second method to test the coating adhesion is using a stylus or loop that an increasing amount of weight is applied until the coating is removed from the substrate. The third method called pull-off adhesion, measures the amount of tensile stress to pull the coating off the substrate. A dolly is glued to the coating surface.
Hardness
The definition of hardness has, in the past, caused misunderstandings within the paint industry. Most coatings are viscoelastic, and hence will indent to some extent.
DIN 55 945 defines hardness as follows:
Hardness is the resistance of a coating to a mechanical force, such as pressure, rubbing or scratching.
In practice, different testing methods are used:
