What is powder coating? Talking about the surface spraying methods commonly used in mechanical design!
What is powder coating? Talking about the surface spraying methods commonly used in mechanical design!
There are two main types of powder coatings: thermoset and thermoplastic polymers.
The most commonly used polymers are polyester, polyurethane, polyester-epoxy, linear epoxy and acrylic. The exact composition of powder coatings varies from manufacturer to manufacturer. The powder is used to form a hard, continuous coating on aluminum profiles to protect the metal from corrosion and provide a durable aesthetic appearance when exposed to various weather conditions.
Powder coatings are mainly used in household appliances, aluminum profiles and other applications, but also in automotive and industrial applications.
There are two main types of powder coatings: thermoset and thermoplastic polymers.
The most commonly used polymers are polyester, polyurethane, polyester-epoxy, linear epoxy and acrylic. The exact composition of powder coatings varies from manufacturer to manufacturer. The powder is used to form a hard, continuous coating on aluminum profiles to protect the metal from corrosion and provide a durable aesthetic appearance when exposed to various weather conditions.
Powder coatings are mainly used in household appliances, aluminum profiles and other applications, but also in automotive and industrial applications.
1. Preparation process and pretreatment
Aluminum can be cleaned by a variety of chemical and mechanical methods prior to the powder coating process. The choice of method depends on the size of the part and the material pretreatment process, which both cleans and improves powder-to-metal bonding. Chemical pretreatment is usually divided into multiple stages, including degreasing of the substrate, etching, decontamination, various washes, and a final chromate treatment.
More recently, methods have been developed to avoid the use of chromates. Methods based on titanium and zirconium chemicals and silanes have similar properties to powder corrosion and adhesion.
Another method of preparing the surface prior to coating is called sandblasting or sandblasting and shot peening.
2. Powder coating process
The most common method of spraying powder coatings on metal objects is to spray powder with an electrostatic gun, which carries positively charged powder and then sprays with mechanical or compressed air, which accelerates the powder to the ground through strong static electricity to charge the artifact. The object is then heated to melt the powder into a uniform film, which is then cooled to form a hard coat. The metal is usually heated before the powder is sprayed onto the workpiece.
Powders can also be applied using specially adapted electrostatic discs.
Another method of spraying powder coatings is called the fluidized bed method. The method involves heating the substrate and then immersing it in an aerated powder-packed bed. The powder melts and sticks to hot objects. Usually when the required thickness is required, the thickness of the coating should exceed 300 microns using this method.
Electrostatic brush (EMB) coating is another coating method used to spray flat materials. The method uses roll-coated powders with high coating speeds and precise coating thicknesses between 5 and 100 microns.
3. Curing
When a thermoset powder is exposed to high temperatures, it begins to melt, flow out, and then chemically react to form a high-molecular-weight polymer with a network structure.
The curing process requires a certain temperature and a certain amount of time to finally achieve full cure and establish the full film properties designed for the material.
Typically, powders are cured at 200°C (390F) for 10 minutes.
