Abrasion & Wear
Use leads to changes in the surface. Various mechanical influences are simulated by different testing methods.
Scratch Test / Scribe Test
Abrasion Resistance, Rub Fastness, or Color Fastness
Mechanical contact with the painted surface can lead to a change in the surface (abrasion). The Crockmeter test is a common testing method for painted surfaces in the automotive industry. This rub test is based on DIN EN ISO 105-X12, which is actually used to test the rub fastness of textiles. A standardized fabric or a special felt is rubbed over the surface for a defined number of strokes. At the end of the test, the fabric is visually examined for possible staining and the painted surface for premature wear. A Crockmeter test is also suitable for simulating a combined exposure to water or other media during mechanical resistance testing, thereby significantly accelerating the aging of a surface.
Painted buttons or printed control elements, however, are preferably tested with an Abrex type device (DIN EN 60068-2-70). Actuation is simulated by a silicone finger with defined contact pressure and lateral displacement, with a fresh rubbing fabric always located between the silicone finger and the surface to be tested. This fabric can also be exposed to a test medium.
The determination of abrasion resistance according to the Martindale method is regulated in standard DIN EN ISO 12947 and is used particularly for textile fabrics such as seat covers. The surface is assessed for sample destruction, surface alteration, or mass loss. The number of abrasion cycles (wear cycles) at which changes were observed is specified.
Stone Chip Test
The resistance of automotive coatings to stone chips is of particular interest to the automotive industry. For simulation, in a stone chip test according to DIN EN ISO 20567-1, sharp-edged impact bodies (hard cast granulate or small stones) of defined size and shape are shot onto the painted surface with compressed air. The type of impact bodies, the working pressure, the impact time, and the angle of impact are specified in corresponding standards. The assessment of stone chip resistance is carried out by visual comparison with images.
Steam Jet Test
The steam jet test according to DIN EN ISO 16925 serves to assess the adhesion of coatings. The steam jet test originated from complaint cases after cleaning cars with high-pressure cleaners or steam jet cleaners. For the test, the paint is first scribed or milled down to the substrate in the shape of a St. Andrew’s cross. Subsequently, the edges of the St. Andrew’s cross are treated with a pressurized water jet under defined conditions. The damage pattern after the steam jet test is evaluated by comparison with image panels of different damage levels.