ABSTRACT
The most widely used adhesion tests for paints, especially in the automotive industry, are Crosshatch tests [1]. For instance, in the General Motors test, a pattern of 100 small squares 1.5 x 1.5 mm2, is cut through the paint into the base metal using a specially designed tool. The hatched area is then tested by adhesive tape and the number of paint squares that have come off is recorded. Other tests that exist are the nickel scratch test, impact tests, bend tests, pull-off tests, and the like. It is not the purpose of this paper to review any of these tests in detail. However, the general comment that can be made is that in all existing tests for paints, the mechanical properties of the paint play an important and sometimes dominant role. For instance, in impact testing of painted automotive steels, failure is often observed to occur at the interface between the phosphate crystals and the metal, and not between the paint and the phosphate crystals. The mechanical properties of the paint are important here as
the paint absorbs the impact energy and transmits part of it to the phosphate-metal interface.
