Determination of Adhesion by Lattice Grooving Method

In order to test the adhesion of the coating film directly on the utensils or on the test panel, the grid cutting method (cutting method) can be used. For example, BHAM would recommend this method for the determination of paint film adhesion directly on objects.

The process of the test is as follows: use a sharp knife to cut 4 to 5 parallel strips with an interval of 1 mm, and then perpendicular to the cut strips, cut out the same number of strips and the same distance between them. Grooving. The method of holding the knife should be as shown in Figure 113. Cutout induction deep into the ground.

If the adhesion is good, a uniform grating that does not come off the metal can be obtained (Figure 114). Depending on the adhesion, one to several squares may come off the metal. When the adhesion is low, the paint film can be peeled off from almost all grids (Figure 115).

When testing thick coatings and coatings made of some polymeric resins, the distance between the notches shall be increased to 2 mm. In the case of poor adhesion, the coating film will peel off from the metal.

The shedding of the paint film depends on the distance between the cuts. The smaller this distance is, the easier it is for the paint film to fall off from the bottom surface.

In the case of very good adhesion, even if the distance between the grooves is not large (less than 0.5 mm), the paint film will generally not fall off from the bottom surface.

CB Yakubovich and TH Vorogushin (THnn-4) proposed a portable instrument for measuring adhesion by using grid cutting grooves, using this instrument to immediately cut square holes of various sizes on the surface grid.

This instrument (Fig. 116) consists of a box with a blade 2; the blade is mounted on an axis 3 at an angle to the horizontal. Liners 4 of different thicknesses (0.5; 1,0; 1_5; 2.0 mm) are inserted in the gap between the blades. On the box cover, there is a rubber pad 5, which leans against the edge of the knife and is used as a shock absorber when the paint film is cut.

In order to prevent the rubber pad from being cut by the blade, a white iron cover plate 6 is placed on the blade. The instrument is also equipped with a handle 7 .

The procedure for measuring adhesion is as follows. Use the handle to carve vertical grooves on the coating film with strong pressure. The result is a grid with rectangular perforations.

The degree of adhesion of the paint film to the surface can be judged by the number of grids of any size that come off the surface during cutting, or by the various auxiliary effects (curve test, impact test) used when the paint film is later tested. It is judged by the number of grid pieces falling off from the surface later.

More recently, this bladed instrument has been replaced by the needle of the phonograph (Fig. 117).