Adhesion refers to the mutual attraction of the contact parts of two different substances, Dacrocoating adhesion refers to the degree of adhesion between the coating or paint film and the substrate. Adhesion is an important index of coatings, and the firm adhesion of paint film is an important basis for the protection of Dacro coatings. The adhesion of the paint film depends on the selected coating base material, but also on the surface pretreatment of the substrate, the construction method and the maintenance of the film has a very important relationship, for example, in the wet, rust, grease metal surface painting, adhesion is poor. Therefore, the determination of film adhesion by coating, coating, anticorrosion and other industries are widely concerned.

At present, the main methods of coating adhesion test are ring adhesion test method, grid adhesion test method and pull adhesion test method. Each of the three test methods has its own characteristics and adaptability.

Looped adhesion test method

Method INTRODUCTION: The needle with sharp Angle penetrates to the substrate, applies a certain load, and moves at a constant speed while making a circle with a certain rotation diameter. The adhesion result is evaluated according to the damage area of the film caused by the circle.

Common standard: GB/T 1720-1979

Rating method: The ring adhesion is divided into 7 grades, and the intact degree of the paint film is checked in order. The adhesion decreases successively from grade 1 to grade 7, and grade 7 is the worst.

Method characteristics: This method is suitable for a variety of single coating adhesion determination, is an indirect determination of the method, not only the adhesion, but also the resistance of the deformation and destruction of the coating, but the operation is simple and fast.

Grid adhesion test method

Method Introduction: It is a test method to evaluate the resistance of the coating from the substrate by cutting the coating through the substrate with a rectangular grid pattern. The result evaluation method is evaluated by the coating shedding area. The cutting distance depends on the coating thickness and the substrate type.

Common standards: GB/T 9286-1998, ISO 2409-2013

Rating method: Under good lighting environment, visual inspection test surface coating peeling condition. The adhesion force is divided into 6 grades, from grade 0 to grade 5, and grade 5 is the worst.

Method features: The method is suitable for measuring the thickness of the coating less than 250mm, can also be used for the determination of multiple coatings, but because it is not easy to judge the adhesion between the coating and the substrate or between the coatings, so it is mostly used for the determination of single coating. Grid method also belongs to indirect test method, simple operation, wide application.

Pull method adhesion test method

Method Introduction: The adhesion force of the pulling method is the force required to determine the adhesion failure between the coatings or between the coatings and the substrate by applying a vertical and uniform tensile force on the bonding surface of the sample at a specified speed. The adhesion force is usually expressed by the measured tensile force per unit area.

Method Introduction: The adhesion force of the pulling method is the force required to determine the adhesion failure between the coatings or between the coatings and the substrate by applying a vertical and uniform tensile force on the bonding surface of the sample at a specified speed. The adhesion force is usually expressed by the measured tensile force per unit area.

Common standards: GB/T 5210-2006, ISO 4624-2016

Rating method: The adhesion force of the pulling method is expressed by the failure strength and failure nature, and the failure strength is expressed by the ratio of the load when the sample is pulled to the area of the test column, which is calculated as MPa. The nature of the damage was determined by visual inspection of the damage surface. The following types of damage are described.

A -- cohesiveness failure of substrate;

A/B -- Adhesion failure between the first coating and the substrate;

B -- cohesive failure of the first coating;

B/C -- Adhesion failure between the first coating and the second coating;

n -- cohesive failure of the NTH channel coating of the composite coating;

n/m -- adhesion failure between the NTH coating and the MTH coating of the composite coating;

-/Y -- breakage of adhesion between the last coating and the adhesive;

Y -- cohesive failure of adhesives;

Y/Z -- Failure of the bond between the adhesive and the test column.

The method is suitable for thick coating, single coating and multi-coating system, and the method is preferred when the adhesion between coatings is measured. It can be used to study the reasonableness of coating formulation and to evaluate the overall adhesion effect of coating. This method is complicated and can not be tested until the adhesive is completely cured.