Powder coating is a method of coating the surface of a substrate with a powder material, heating it to a fluid state, and then curing it to cover the surface of the substrate to form a protective or decorative coating. Powder coatings have many advantages over traditional liquid coatings, such as better environmental performance, thicker coatings can be obtained with one application, and various styles.

Powder coating application is still more complicated in some aspects, and it is necessary to select appropriate products and coating processes according to different needs. So how to do powder coating?

1. Steps of powder coating

1.1 First determine the type of substrate to be coated. Powder coatings are divided into two types: thermoplastic and thermosetting. It is necessary to select suitable powder coatings according to different substrates to achieve the best coating effect.

1.2 Before painting, disassemble all threads or lubrication interfaces, and all parts that do not need to be painted. It sounds simple, but many people forget this step. The powder coating will adhere to everything, including screws, nuts, bearings and other parts that do not need to be painted.

1.3 Thoroughly clean the metal surface. Use shot blasting or sandblasting to treat cemented carbide to remove dirt and rust on the surface. Use chemical solvents to clean the grease and coating on the surface, and can be polished. If necessary, aluminum, magnesium and other soft metal alloys can be cleaned with a solvent and polished with a wire brush.

1.4 Apply powder coating to the surface of the substrate. By using a spray gun or a compressed air sprayer, the charged powder coating can be adsorbed on the surface of the grounded substrate. The price of the spray gun is based on the supplier, and a minimum of US$100 is recommended. In the experiment, the powder can be sprayed directly on the surface of the metal plate.

1.5 Choose an appropriate temperature to cure the powder coating attached to the substrate. The oven can be used for curing. Generally, it can be applied to metal substrates of relatively small size. Large-scale substrates can also be cured by infrared or other flameless heat sources. Under normal circumstances, the object is heated to 175～190℃, about 10～15min, and then cooled.

2. The difference between thermoplastic powder coating and thermosetting powder coating

2.1 Thermoplastic powder coatings can be re-melted and solidified, while thermosetting powder coatings cannot be re-melted and solidified after solidification. This is the most obvious difference between the two.

Just like the names of the two, the reason why thermosetting powder coatings cannot be recured is an irreversible chemical reaction. In contrast, thermoplastic powder coatings do not undergo chemical reactions during the curing process.

2.2 The choice of coating depends on the characteristics of the substrate to be coated. Thermoplastic and thermosetting powder coatings are used on different substrates due to different chemical properties.

Thermosetting powder coating: It can strengthen the integrity of the substrate, is suitable for the substrate that will be severely worn, and can provide chemical resistance and heat resistance.

Thermoplastic powder coating: It can provide strength and flexibility, and is commonly used in plastics and mechanical parts.

2.3 About the advantages and disadvantages of thermosetting powder coatings. Generally thermosetting powder coatings are used on heat-resistant substrates.

Advantages: beautiful coating; low cost; good coating stability and heat resistance.

Disadvantages: The irreversible curing process means that the coating cannot be recycled, and it is difficult to melt and solidify the second time.

2.4 About the advantages and disadvantages of thermoplastic powder coatings. Thermoplastic powder coatings are generally used on plastic and durable substrates like park benches, and they are also widely used on the outer surface of metal pipes.

Advantages: high lubricity; able to re-melt and solidify; increase impact resistance

Disadvantages: Generally speaking, the cost is high; heating may melt.