Test Method for Adhesion Properties of Toyota TSH1503G Paint Film

In the "Toyota TSH1503G Test method for the adhesive property of paint film" standard developed by the Toyota vehicle company, a procedure for determining the adhesive power of vehicle paints is described.

The adhesion of a coating refers to the strong bond between the coating and the substrate of a material. Most coatings need to form a strong bond and adhere to the substrate for a long period of time after curing and film formation is complete. Film formation plays an important role in adhesion. Various factors such as shrinkage and pressure affect film formation after curing. The bond strength between the coating and the substrate depends on the following properties of the material:

• Adhesion: The bonding strength of an adhesive to the substrate surface
• Cohesion: The strength of the bond between cohesive particles

Adhesion is one of the key properties in the paint and coating industry. It ensures that the layer or paint film remains attached to the surface for a long time, especially under aggressive conditions. The nature of adhesion is directly related to the durability and quality of the coating. Key elements that regulate the adhesion of coatings to the substrate include:

• Substrate coating interface
• Composition of coatings
• Film formation (must be such that the interface is as strong as possible)

According to one theory, two materials stick together due to gravitational forces. These forces exist between surface molecules and adhere to their interfaces. These are intermolecular forces. The surface forces developed are defined as secondary forces. For these forces to develop, dye molecules must make close molecular contact with the substrate surface.

Acid-base interactions and hydrogen bonds can also contribute to intrinsic adhesion forces. To achieve good absorption, it is important to establish constant contact between the paint film and the bonded material.

Cross-cut testing, described in the Toyota TSH1503G standard, is a method for determining the resistance of paints and coatings to separation from substrates using a tool that penetrates into the substrate by cutting a right-angle lattice pattern into the coating.

With this method, it is possible to perform a rapid pass/fail test. When testing a multilayer system, determination of the resistance to separation of different layers can be carried out. While performing this test, a grid-shaped incision is made in an area of ​​at least 10 x 10 cm, using a cutter or a suitable metal knife, down to the bottom layer. Evenly spaced cuts (8-10 mm) are created horizontally and vertically to create a lattice pattern on the surface of the test area. Adhesive tape is applied to cover the cut area and removed vigorously. The area is observed to determine the result.

Adhesion is classified according to standards as follows:

• ISO 0: The edges of the cutouts are completely smooth, none of the squares in the grid are separated. The surface is suitable for painting after the necessary preparations.
• ISO 1: Small coating flakes are broken off at the intersections of the cuts, a 5 percent cross-cut area is affected. The surface is suitable for painting after the necessary preparations.
• ISO 2: Small coating flakes separated at the intersections of the cuts along the edges, with a 5-15 percent cross-cut area affected. The surface is suitable for painting after the necessary preparations.
• ISO 3: Paint partially or completely flaked along edges or some frames partially or completely separated, with a cross-cut area of ​​15 to 35 percent affected. A bonding fixative primer is applied to the grid before painting, and after drying the test is repeated to evaluate adhesion. If the values ​​improve, the surface can be painted after a coat of fixative primer. Otherwise, part or all of the surface will be scraped off before repainting.
• ISO 4: Paint has flaked in large stripes along the edges of the cuts, or some squares have been partially or completely separated, with a cross-cut area of ​​35 to 65 percent affected. The surface must be partially or completely scraped before painting.
• ISO 5: Any degree of flaking not falling within classification ISO 65 in which the separated paint exceeds 4 percent of the crosscut area. The surface must be completely scraped before painting.

Among the numerous testing, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides testing services defined in the "Toyota TSH1503G Test method for the adhesion property of paint film" standard, with a trained and expert staff and advanced technological equipment.