Due to the blooming of household appliances, there are many kinds of surface treatment methods for galvanized sheet, and the performance requirements are also different. Among them, fingerprint resistant treatment is the most widely used.
1) The role of fingerprint resistance
Fingerprint resistant treatment is to coat a thin and transparent organic resin film on the surface of galvanized sheet, which can prevent the fingerprint of operators from adhering to the product in the production process of galvanized sheet, and affect
the appearance of the product. At the same time, it can also improve the corrosion resistance of the product, improve the lubricity of the forming process, and be used as the adhesive substrate for subsequent coating.
2) Fingerprint resistant coating
The fingerprint resistant coating should be carried out after passivation, so as to make the product have good appearance and good corrosion resistance
There are many kinds of water-soluble resins, such as
acrylic resin, polyurethane resin, etc. Acrylic resin has light color, high transparency, good heat resistance, corrosion resistance, flexibility and processability. At the same time, it has strong adhesion to galvanized sheet. It is widely used in fingerprint
resistant coating. Polyurethane resin has strong corrosion resistance and is widely used.
3) The process of fingerprint film formation
The fingerprint resistant coating is applied on the surface of galvanized sheet by roller coating method.
The organic resin in the coating is suspended in the aqueous phase with tiny particles. When drying, the water gradually evaporates and the volume decreases. These dispersed polymer particles gradually approach each other. The capillary pressure between
the particles forces the particles to squeeze. With the evaporation of water, the pressure continues to increase, which makes the particles deform. Finally, the particles fuse with each other to form a continuous organic film 。 Therefore, the drying temperature
and time after fingerprint treatment are very important, otherwise it will cause the poor curing of the film and the adhesion between the galvanized sheets inside the coil. Generally, the film thickness is about 1 μ m, the plate temperature is about 110
℃ when drying, and then it is cooled to room temperature for coiling.
4) Composition of fingerprint resistant film
The fingerprint resistant film is divided into reaction layer, concentration layer and lubrication layer, which give the anti
fingerprint film corrosion resistance, lubrication, fingerprint resistance, adhesion and other properties respectively.
After the passivation solution was coated on the surface of galvanized sheet and dried, the film forming process was divided
into four stages
Stage I: wet film coating: the effective components are evenly dispersed in the water medium;
Stage II: evaporation of unbound water in wet film;
Stage III: separation of surface dispersant → fusion of particles;
Stage IV: ideal film-forming state, complete separation of bound water / dispersant, full crosslinking and complete fusion of particles.