Mar Resistance of Paint Coatings by Nanoscratch Testing

Mar can be defined as a physical damage that typically occurs within a few micrometers of the surface of the topcoats; these damages are commonly the cause of the changes in appearance seen on the paint coatings¹.

Mar is thus one of the big concerns of the automotive coating sector.

Some reasons for mar include keys, branches, blowing sand and fingernails. The car wash is however considered as the main cause¹ as it is one of the few repeated activities for most car owners.

The purpose of this article is to show a mar behavior analysis methodology with the aid of the Anton Paar Nanoscratch Tester. This methodology, which allows an objective quantitative measurement of the mar behavior on automotive paint coating, will be comprehensive in this article together with a typical example. An example of progressive load scratch on automotive clearcoat is illustrated in Figure 1. The figure also illustrates a Panorama image, which is synchronized with depth signals and load recorded during the scratch procedure.

This test methodology is according to the International Standard D 7187-05.

Figure 1. Panorama image showing typical scratch track on an automotive clearcoat together with recorded signals of penetration depth (Pd) and residual depth (Rd). Vertical line indicates critical load (Lc1).

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This information has been sourced, reviewed and adapted from materials provided by Anton Paar GmbH.

For more information on this source, please visit Anton Paar GmbH.