The cross-cut adhesion of the coating film can be determined according to the method in the national standard "Cross-cut test of paint and varnish film" (GB/T9286--88). This standard is equivalent to the international standard IS024o9-1972 "Paints and varnishes - cross-cut test".
This standard specifies empirical test methods for evaluating the delamination performance of paints, varnishes and related products. This is one of the performance measurement methods that can be used among the factors that affect the adhesion of the coating to the substrate. However, this method should not be regarded as a method of measuring adhesion itself.
This standard specifies a simple empirical test procedure for evaluating the resistance of coatings of paints, varnishes and related products to detachment from the substrate when the coating grid pattern is cut and just penetrates the substrate. .
(1) Instrument
1. Cutting tool: Can use fruit seed single-knife mechanical cutting device or single-knife or multi-knife manual cutting tool, or other suitable instruments. No matter which one is used, it should be based on the cutting line with high uniformity.
② Cutting edge standard: cutting edge angle 30°, cutting edge thickness 50~100µm, for example 80µm. The single-edge and multi-edge tools shown in Figure 6-19 are one of the applicable tools for this standard.
③Soft brush
④Test plate: thin steel plate, tinplate plate, aluminum plate or glass plate that shall meet the requirements of GB/T9271.
(2) Test procedure
① Unless otherwise specified, the test should be carried out in an environment with a temperature of 23°C±2°C and a relative humidity of 5o%±5%.
② Number of cuts: The number of cuts in each direction of the cross-cut pattern should be 6 or 11, which should be agreed upon by relevant parties.
③ Cutting distance: The cutting distance in each direction should be 1mm or 2mm at the same time. The selection of the spacing should be based on the nature of the coating and agreed upon by the relevant parties.
④ Cutting method: install the Jj tool that has passed the inspection, and adjust the balance of the knife tube. Then add a magnetic code of appropriate quality on the upper part of the tool so that the edge of the knife can just penetrate the coating and touch the substrate when cutting. If the cutting layer does not touch the substrate, the test is invalid. Use a soft brush to gently reciprocate 5 times along the two diagonal directions of the grid.
⑤ Test repeatability: the test shall be completed at least at 3 different positions on the test board. If the test results of the 3 positions are judged to be inconsistent by the following grading method, the test shall be repeated at the other 3 positions. Simultaneously record all results.
(3) Evaluation
① Table 6-3 gives the classification of the 6-level evaluation, the first 3 levels can usually meet the general purpose, and use "pass" or "fail" to evaluate. In special cases, 6 levels of classification and evaluation are required.
② Inspection: Use normal vision (or corrected normal vision) to view the cut surface of the test coating, compare it with the descriptions and drawings in Table 6-3, and grade according to the comparison results.
If in special circumstances, it is necessary to use a magnifying glass to observe and measure, then whether to agree to use a magnifying glass with a multiple should be agreed upon by the parties concerned.
