Calo Test

  Schematic functional principle and two light microscopic images Copyright: © IOT Scheme of calo test (a), light optical microscope image of two different calottes: multilayer coating (b) and single layer (c)

The intention of calo testing is to determine the coating thickness. For this the projection area of a ball in a coating measured by light microscopy is used. The coating thickness can be determined via the geometric coherences of projection area and ball radius. A hardened steel ball of defined diameter is punctually situated on a coated surface in order to grind into the coating. Many coatings are harder than the steel ball, so diamond suspension is additionally used to support the grinding process. The grinding time can be set in discrete increments. Depending on the specimen geometry, various grinding patterns occur; for example, concentric circles appear on even specimens. Once the coating has been abraded off, the projection surface can be evaluated.

⦁ Determination of coating thickness
⦁ Examination of bond strength
⦁ Wear behaviour of the coating