Generally, coatings are applied on a substrate to protect the surface. In addition, they enhance the appearance of the substrate in terms of gloss and color. Scratches not only greatly reduce the surface aesthetics of a coated product but can lead to premature failure of the substrate. The visual detection of wear and tear, that is reduced surface aesthetics, is straightforward. Conversely, the relationship between scratch test, scratch resistance, chemical composition and coating properties is more intricate.
Scratch resistance is not uniquely defined, and is difficult to measure. Different terminologies are used, ranging from marring for optical defects towards friction, wear, erosion, abrasion and cracking for mechanical defects.1,2 The scratch resistance can be evaluated in terms of gloss reduction, haze, magnitude of deformation, resistance towards deformation, weight loss or color change of the substrate.
The relationship between deformation and surface properties of both the scratch stylus and coated substrate is complex.3 Briscoe et al.