Powder coating is a coating applied as a free-flowing dry powder. The coating is usually electrostatically applied and then cured with heat, allowing it to flow and form a surface film on the metal.
There are two main types of powder coatings: thermoset powder coatings (polymers) and thermoplastic powder coatings (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 all weather conditions.
Powder coatings are mainly used in areas such as household appliances, aluminum profiles, as well as in automotive and industrial applications.
Powder Coating Properties Since powder coating does not have a liquid carrier, it can produce thicker coatings than traditional liquid coatings. The coating process releases very little volatile organic compounds (VOCs). Several powder colors are available before curing together, allowing you to mix colors and create special effects in a single coat.
While it is easier to apply a thick coat that dries to a smooth surface without texture, it is not so easy to apply a smooth film.
The main advantage of powder coatings is the ability to reuse overspray. Many of the recognized advantages of powders over liquid coatings (other than PVDF), such as hardness and gloss, are actually properties of the polymer.1. Preparation process and pre-processing
Aluminum cleaning can be carried out by various chemical and mechanical methods before powder coating. The choice of method depends on the size of the part and the material. The pre-treatment process cleans and improves the adhesion of the powder to the metal. Chemical pre-treatment is usually divided into several stages, including degreasing, pickling, dedusting, various washes and final chromating of the substrate.
Recently, methods have been developed to avoid the use of chromates. Titanium and zirconium based chemistries as well as silane based approaches have similar characteristics in terms of corrosion and powder adhesion.
Another method of surface preparation prior to coating is known as sandblasting or shot blasting.2. Powder Coating Process
The most common method of powder coating metal objects is to spray the powder with an electrostatic gun that charges the powder with a positive charge, then sprays it mechanically or with compressed air and accelerates it with a strong electrostatic charge towards the grounded workpiece. The object is then heated to melt the powder into a uniform film, which is then cooled to form a hard coating. The metal is also 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, called the fluidized bed method, involves heating the substrate and immersing it in an air-filled compacted layer of powder that melts and adheres to the hot object. Typically, the coating thickness using this method should exceed 300 microns when the required thickness is required.
Electrostatic brush coating (EMB) is another coating method for spraying flat materials that uses roller powder coating with a relatively high coating speed and accurate coating in thicknesses of 5 to 100 microns.3. Curing
When thermosetting powder is exposed to high temperatures, it begins to melt, flow out, and then chemically react to form a network of high molecular weight polymers.
The curing process requires a certain temperature over a period of time to eventually achieve full cure and set all the film properties for which the material is intended.
Typically, the powder is cured at 200 °C (390 F) for 10 minutes.
Powder coated aluminum application
Powder coated aluminum is a building material used in many construction projects. Powder coating aluminum helps enhance the metal's ability to resist corrosion from the elements. This characteristic makes the material ideal for use. outdoors.
Architectural powder coatings are available in a variety of colors, including white, to achieve the desired effect. Industrial use is one of the largest markets for powder coatings with growing applications in the automotive industry.
The choice of powder coating depends on the application, not just personal preference. Powder coatings do not contain solvents and no hazardous waste is generated during the coating process. The main advantage of powder coatings is that overspray can be recycled, making powder coatings an environmentally friendly method.