Comparison of Adhesion Test Methods: Circle Method, Cross Method and Pull Method

What is the circle method?

The circle method is to use the circle method adhesion Tester to test the adhesion, and evaluate the adhesion according to the integrity of the paint film within the scratch range of the circular rolling line, and the results are expressed in grades. Instruments and test materials include the circle method adhesion Tester, rotating needle, 4 times magnifying glass, soft brush.

The circle method is suitable for the determination of the adhesion of various single coatings and is widely used.

What is the grid method?

The cross-hatch method is to evaluate the resistance of the coating to separation from the substrate, or the ability of the multi-coating system to resist separation from each other, when the multi-coating is cut according to the lattice pattern and just penetrates the coating to reach the substrate. Grading representation. Instrument and test materials include: 6-blade cutting knife, transparent pressure-sensitive tape, soft brush

The cross-cut is used to measure coatings with a thickness less than 250μm. Although it can also be used for the determination of multi-coatings, it is often used because it is difficult to judge whether it is the adhesion between the coating and the substrate or the adhesion between the coatings. For the determination of single coatings.

What is the pulling method?

The pull-off method is to apply a vertical and uniform tensile force on the cemented surface of the sample at a specified speed to measure the force required when the adhesion between the coatings or between the coating and the substrate is broken, in N/cm2 express. Instruments and test materials include Tensile Testing Machines, fixtures, test columns, centering devices, adhesives

The pull-off method is suitable for thicker coatings (such as putty), both single-coat and multi-coat systems, but it is preferred when measuring the adhesion between coatings.

Advantages and disadvantages of the three major adhesion test methods

1. Both the circle-marking method and the cross-cutting method are indirect measurement methods. What is obtained is not only the adhesion, but also the deformation and resistance of the coating when it is damaged. However, the operation is simple and quick, and it is widely used.

2. The pull-off method is a direct measurement method. It can express the coating adhesion with numbers. It is a good method to investigate whether the coating is reasonable and comprehensively evaluate the overall adhesion effect of the coating. Through the inspection of adhesion, the composition of the coating can also be checked , especially whether the use of resin is reasonable. However, the process of the pull-off method is more complicated, and it is necessary to wait until the adhesive is completely cured before testing.