BGD 520-2 Automatic Scratch Tester: ISO 1518-2 - Variable-loading
Coatings and paints can protect, decorate substrate or conceal the defects of substrate, and these three functions are related with coatings hardness. And hardness is the important performance for paint mechanical strength, as well as the important indicator to judge paint quality. One of important indicators to evaluate coatings hardness is scratch tester.
ISO 1518 (Paints and varnishes -- Determination of scratch resistance) specifies a test method for determining under defined conditions the resistance of a single coating or a multi-coat system of paint, varnish or related product to penetration by scratching with a scratch stylus loaded with a specified load. Penetration of the stylus is to the substrate, except in the case of a multi-coat system, in which case the stylus can penetrate either to the substrate or to an intermediate coat.
This test has been found to be useful in comparing the scratch resistance of different coatings. It is most useful in providing relative ratings for a series of coated panels exhibiting significant differences in scratch resistance. Before 2011, there was only one standard which was used to evaluate paint scratch resistance, which against to evaluate scientifically to paints scratch resistance under different applications. After revision of this standard in 2011, this test method was divided two parts: One is constant-loading, i.e the loading to panels is constant during the scratch test, and the test results is shown as max. weights which don't damage coatings.
The other is variable loading, i.e. the loading on which stylus loads test panel is increased continuously from 0 during the whole test, then measure the distance from finial point to the other point when the paint appear scratch. Testing result is shown as critical loads.