Cross-cut

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The worst possible result - Gt 5 . The white paint has flaked off both along the cut edges and in the area of ​​the sections.

Using the cross-cut in accordance with DIN EN ISO 2409 the adhesion strength (can adhesion ) of coatings (such as a painted be estimated surface). The test method is explicitly not used to measure the adhesive strength. The deduction test according to DIN EN ISO 4624 must be used for this.

description

With a cross-cut, six parallel cuts are made on the coating with a special cross-cut knife (several cutting edges) or a single-cutting device (e.g. cutter knife with or without a template). At a right angle to the resulting cuts, six more incisions are made so that a uniform square pattern is created. All cuts must go right down to the substrate and scratch or scratch it, but without damaging it excessively. The test can be carried out manually or with a motor-driven device.

The distance between the cuts is one to three millimeters , depending on the layer thickness of the coating and the hardness / type of substrate.

  • For layers up to 60 micrometers thick, a grid spacing of 1 millimeter (hard surfaces such as metal ) or 2 millimeters (on soft surfaces such as wood) should be selected.
  • For layer thicknesses between 61 and 120 micrometers, a grid spacing of 2 millimeters is required.
  • From a layer thickness of 121 to 250 micrometers, 3 millimeters are used.
  • The cross-cut can no longer be used above 250 micrometers. A cross-cut can be used here in accordance with DIN EN ISO 16276-2.

Any loose particles (of the coating) from the cutting must then be removed. A soft brush, compressed air or nitrogen or adhesive tape can be used for this. Contrary to previous editions of the standard, the adhesive strength of the adhesive tape is no longer required (from 2013). The adhesive tape must be stuck on parallel to one direction of the cuts and removed again abruptly (0.5–1 seconds) at an angle of 60 ° within 5 minutes.

Finally, the remaining grid is examined. Depending on the condition, a distinction is made between cross-cut characteristic values ​​from 0 (very good) to 5 (very bad), abbreviated as Gt 0 to Gt 5. In addition to this classification procedure, a yes / no test can also be carried out on the respective specifications. In the area of ​​corrosion protection, characteristic values ​​of Gt 0 or Gt 1 are often accepted.

Norms and standards (as of September 10, 2018)

  • DIN EN ISO 2409: 2013-06 Coating materials - Cross-cut test
  • DIN EN ISO 16276-2: 2007-08, Corrosion protection of steel structures by coating systems - Assessment of the adhesion / cohesion (adhesive strength) of a dry coating and criteria for its acceptance - Part 2: Cross-cut and cross-cut test
  • DIN EN ISO 4624: 2016-08 Coating materials - Tear-off test to determine the adhesive strength

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