1 Scope

1.1 This standard specifies a method for evaluating the resistance of a coating to detach from a substrate when cutting the coating into the substrate in a right-angle grid pattern. a test method. The performance measured using this empirical test procedure depends on various factors in addition to the adhesion of the coating to the previous coating or substrate. Therefore this test procedure cannot be considered as a method of determining adhesion.

Note 1: Although this test is mainly specified for laboratory use, it is also applicable to field testing.

1.2 The method specified may be used as a pass/fail or, where appropriate, as a six-level classification test (see 8.3). When used in a multi-layer coating system, it can be used to evaluate the resistance of each coat to detachment from each other coat in the coating system.

1.3 This test can be carried out on objects coated with topcoat and/or on specially prepared specimens.

Although this test method is suitable for coatings on hard substrates (steel) and soft substrates (wood and plastics), these different substrates require a different test procedure (see Section Chapter 7).

This test method is not applicable to coatings with a coating thickness greater than 250 μm, nor to textured coatings.

Note 2: When applied to coatings designed to have uneven patterned surfaces, the results obtained by this method will have greater deviations.

2 Quoted standards

The provisions contained in the following standards constitute provisions of this standard by being quoted in this standard. At the time of publication of this standard, the versions indicated were valid. All standards are subject to revision and parties using this standard should explore the possibility of using the latest version of the standard listed below.

GB/T 1727-92 General preparation method of paint film

GB 3186-82 (89) Sampling of coating products (neq ISO 1512: 1978, etc.)

GB/T 13452.2-92 Determination of film thickness of paints and varnishes (eqv ISO 2808:1974)

3 Supplementary information required

For any specific In terms of application, the test methods specified in this standard need to be improved with supplementary information. Items of these supplementary materials are listed in Appendix A.

4 Instruments

4.1 Cutting knives

It is particularly important to ensure that the cutting knives have the specified shape and the blade is in good condition.

4.1.1 Some suitable cutting tools are listed below, as shown in Figures 1a) and 1b):

a) The blade of a single-edged cutting tool is 20°~30° , and other dimensions, as specified in Figure 1a).

b) Multi-edged cutting tool with six cutting knives, the blade spacing is 1mm or 2mm, as specified in Figure 1b).

In all cases, single-edged cutting tools are the preferred tool, i.e. suitable for various coatings on hard or soft substrates. Multi-edged tools are not suitable for thick coatings (>120μm) or hard coatings, or coatings applied to soft substrates.

4.1.2 4.1.1 The specified tools are suitable for manual operation, although this is the more common method. The cutter may also be mounted on a motor-driven instrument to obtain a more uniform cut. The operating procedures for applying the instrument shall be agreed between the parties involved.

4.2 Guide and blade spacer devices

In order to cut the space correctly, when using a single-edged cutting tool, a series of guide and blade spacer devices are required. A suitable device is as shown in the figure 2 shown.

4.3 Soft brush

4.4 Transparent pressure-sensitive adhesive tape

The adhesive tape used is 25mm wide and has an adhesive force of (10±1) N /25mm or agreed upon.

4.5 Visual magnifying glass

Handheld type, magnification is 2 times or 3 times.

5 Sampling

Take representative samples of the tested products in accordance with the provisions of GB3186.

6 Test Plate

6.1 Substrate

Unless otherwise agreed, select a substrate from those specified in GB/T 9271. The test panel should be flat and without deformation. The size of the test panel should be such that it allows the test to be carried out in three different positions. The distance between these three positions should not be less than 5 mm from each other and from the edge of the test panel.

When the test panel is made of softer materials (such as wood), its minimum thickness should be 10mm. When the test panel is made of hard material, its minimum thickness shall be 0.25mm.

Note 3: A rectangular test plate with a size of approximately 150mm × 100mm is suitable.

Note 4: When the test panel is made of wood, the direction and structure of the wood grain may affect the test, and obvious wood grain will make the evaluation impossible.

6.2 Treatment and coating of test panels

Unless otherwise agreed, each test panel shall be processed according to the provisions of GB/T 9271, and the sample plate shall be prepared according to the provisions of GB/T 1727.

6.3 Drying of the sample

Carry out according to the provisions of Chapter 7 of GB/T1727-92.

6.4 Determination of coating thickness

Measure the thickness of the dry coating in μm according to one of the methods specified in GB/T 13452.2. The measurement should be carried out on the coating as close as possible to the position where the cutting test is to be measured. The number of coating thickness measurements depends on the method used.

7 Operating steps

7.1 General provisions

7.1.1 Test conditions and number of tests

Unless otherwise agreed, the test conditions shall be as follows: Provisions of GB 9278;

Note 5: During on-site testing, environmental conditions will be allowed.

Carry out tests in at least three different positions (see 6.1) on the sample plate (see also 8.1). If the three results are inconsistent and the difference exceeds one unit level, repeat the above test at three or more different locations. If necessary, use another sample and record all test results.

7.1.2 Condition adjustment of the sample

Unless otherwise specified, the sample shall be placed under the conditions specified in GB9278 for at least 16 hours before the test.

7.1.3 Number of cuts

The number of cuts in each direction of the cutting pattern should be 6.

7.1.4 Spacing of cuts

The spacing of cuts should be equal in each direction, and the spacing of cuts depends on the coating thickness and the type of substrate, as follows:

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0～60μm: hard substrate, 1mm spacing.

0～60μm: soft substrate, 2mm spacing.

61～120μm: hard or soft substrate, 2mm spacing.

121～250μm: hard or soft substrate, 3mm spacing.

7.2 Cut the coating manually

7.2.1 Place the sample on a hard, flat surface to prevent any deformation of the sample during the test.

7.2.2 Complete manual cutting according to the procedures specified below.

Before the test, check the cutting edge of the tool and keep it in good condition by sharpening or replacing the blade.

If the template is made of wood or similar material, cut at approximately 45° to the direction of the wood grain.

7.2.3 Hold the cutting tool (4.1), make the knife perpendicular to the surface of the sample, apply force evenly on the cutting tool, and use an appropriate spacing guide (4.2) to use a uniform cutting speed on the coating. The prescribed number of cuts is formed. All cuts should be made to the surface of the substrate.

If it is impossible to cut through the substrate because the coating is too hard, the test is invalid and should be recorded truthfully.

7.2.4 Repeat the above operations. Make the same number of parallel cutting lines and intersect the original cutting lines at an angle of 90° to form a grid pattern.

7.2.5 Use a soft brush (4.3) along each diagonal line of the grid pattern, gently sweep backward several times, and then sweep forward several times.

7.2.6 Additional adhesive tape (4.4) is only applied to hard substrates. Pull out a section of adhesive tape at a uniform speed, remove the front section, and then cut off a length of approximately 75mm.

Place the center point of the adhesive tape above the grid, with the direction parallel to a set of cutting lines, as shown in Figure 3, and then press the adhesive tape above the grid area with your fingers. Flat, the length of the adhesive tape should be at least 20mm longer than the grid.

To ensure good contact between the tape and coating, rub the tape firmly with your fingertips. Full contact of the coating color seen through the adhesive tape is an effective display.

Within 5 minutes of applying the adhesive tape, hold the hanging end of the adhesive tape and tear it off smoothly within 0.5 to 1.0 seconds at an angle as close to 60° as possible (see Figure 3).

7.2.7 The adhesive tape can be fixed on the transparent film surface and retained for reference.

7.3 Cutting the coating with a motor-driven tool

If a motor-driven device is used for the cutting tool, the operations specified in the manual operation steps must be followed, especially with regard to the cutting intervals and Number of trials.

8 Presentation of results

8.1 Results are evaluated as follows.

—Soft substrate: immediately after brushing;

—Hard substrate: immediately after peeling off the adhesive tape.

8.2 In a good lighting environment, carefully inspect the cut area of ??the test coating with normal or corrected vision, or as agreed upon by the parties concerned, with a visual magnifying glass (4.5). During the observation process, rotate the sample so that the observation and illumination of the test surface are not limited to one direction. Inspecting adhesive tape in a similar manner is also effective.

8.3 Classify the test surface according to Table 1 by comparing with the illustration.

Table 1 Test result classification

Note 6: The descriptors in Table 1 provide auxiliary guidance.

The six levels of classification are given in Table 1. For general purposes, the first three levels are satisfactory. It is required that the first three levels are also used when assessing pass/fail.

8.4 For multi-coat systems, report any delamination that occurs between interfaces.

8.5 If test results differ, report the results of each test. In the case of multi-layer coating systems, report the location of the peeling (either between coatings or between coatings and substrate).

9 Test Report

The test report should at least include the following contents:

a) All necessary details required to identify the product under test;

b) Indicate the reference to this standard;

c) The terms of the supplementary content in Appendix A, especially the type of cutting tools used;

d) Indicate International standards or national standards, product specifications or other documents referenced to provide supplementary content involved in item c);

e) Test results evaluated according to Chapter 8;

f) Any differences from the prescribed test methods;

Appendix A

(Appendix to the standard)

Required supplementary information

< p>To enable the method to be performed, the items listed in this appendix as supplementary information should be provided as appropriate.

The required information should preferably be agreed upon by both parties involved, and can be partially or fully derived from international standards or national standards or other documents related to the product being tested.

a) Substrate material (including thickness) and surface treatment.

b) The method of application of the test coating to the substrate, including the drying conditions and times of the coating in the case of a multi-layer coating system.

c) Conditions and time for drying (or baking) and placing (if applicable) of the coating before testing.

d) The conditioning time of the sample before starting the test (even if other tests have been completed on the sample beforehand).

e) Whether it is a single coating or a multi-layer coating system, measure the thickness of the dry coating in μm according to the method of GB/T13452.2.

f) The temperature and humidity of the test, if different from those specified in 7.1.1.

g) The test procedure performed, i.e. whether it is a pass/fail or graded test.

h) Type of cutting tool used and method of operation (manual or motor driven).

i) The required (grading) properties of the material according to the classification given in Table 1.