Due to the blooming of household electrical appliances, there are a wide variety of surface treatment methods used by galvanized sheet, and the requirements for performance are also different, among which the most used is fingerprint resistant treatment.
1) Anti fingerprint processing function
Fingerprint resistant treatment is to coat a very thin and transparent organic resin film on the surface of galvanized sheet, which can prevent the fingerprint of operators from adhering to the product and
affecting the appearance of the product during the production and processing of galvanized sheet. At the same time, it can also improve the corrosion resistance of products, improve the lubricity during forming and processing, and serve as the adhesive
bottom layer for subsequent coating.
2) Fingerprint resistant coating
The fingerprint resistant treatment coating is preferably carried out after passivation, so as to work together with the passivation film to make the product not only have
good appearance, but also have good corrosion resistance.
There are many kinds of water-soluble resins that can be used as fingerprint resistant coatings, 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
3) Fingerprint resistant film forming process
Fingerprint resistant coatings are applied to the surface of galvanized sheet by roll coating method. The organic resin in the coating is suspended in the aqueous phase as 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 tightly. With the evaporation of water,
the pressure continues to increase and deform the particles, Finally, the particles fuse with each other to form a continuous organic film. Therefore, the drying temperature and time after fingerprint resistance treatment are very important, otherwise
it will cause poor curing of the coating film and mutual bonding between various layers of galvanized sheets inside the steel coil. Generally, the film thickness is 1 μ M. when drying, the plate temperature is about 110 ℃, 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 fingerprint resistant film corrosion resistance,
lubrication, fingerprint resistance, adhesion and other properties respectively.
After the passivation solution is coated on the surface of galvanized sheet and dried, the film-forming process is divided into four stages:
Stage I: wet film
coating: the effective components are evenly dispersed in the aqueous medium;
Stage II: volatilization of unbound water in wet film;
Stage III: separation of surface dispersant of resin latex particles → fusion between particles
IV: ideal film-forming state, complete separation of bound water / dispersant, full cross-linking and complete fusion of particles.