Cross Cut Test - The most Reliable Method for Estimating Coating Adhesion ISO 2409, ASTM D 3359

Introduction

Cross-cutting is a proven technique for estimating the adhesion of coatings, including painted surfaces. This method, which is carried out in accordance with DIN EN ISO 2409, is explicitly not used to measure the adhesive strength, but rather to estimate it. For an exact measurement, the deduction test according to DIN EN ISO 4624 should be used.

Proceedings

A cross cut involves making six parallel cuts and another six perpendicular scribe cuts on the coating to create a regular square pattern. The cuts must go through to the ground without damaging it too much. The test can be carried out manually or with a motor-driven device.

Coating thickness and grid spacing

The thickness of the coating and the grid spacing affect the process of cross-cutting. For coating thicknesses of up to 60 micrometers, a grid spacing of 1 millimeter (on a hard substrate such as metal) or 2 millimeters (on a soft substrate such as wood) should be selected.
A grid spacing of 2 millimeters is required for coating thicknesses between 61 and 120 micrometers and a grid spacing of 3 millimeters is used for coating thicknesses of 121 to 250 micrometers. Above 250 micrometers the cross cut is no longer applicable, in this case a cross cut test according to DIN EN ISO 16276-2 should be carried out. 

Removal of particles

After completing the crosscut, it is important to remove any loose debris from the cuts. A soft brush, compressed air, nitrogen or adhesive tape can be used for this. Since 2013, the adhesive strength of the adhesive tape is no longer specified, but it should be applied parallel to one direction of the cuts and then removed quickly (0.5-1 seconds) at an angle of 60° within 5 minutes.

Evaluation of the grid

At the end of the crosscut, the remaining grid is examined. A distinction is made here between cross-cut characteristic values from 0 (very good) to 5 (very bad), abbreviated Gt 0 to Gt 5. In addition to this classification procedure, a yes/no test can also be carried out for the respective specifications. Characteristic values of Gt 0 or Gt 1 are often accepted in the field of corrosion protection.