Powder coating service

“Powder coating technology” is something that everyone has heard of, but not everyone understands what this technology is. In today’s article, we will help you better understand what powder coating is, how it is done, and the advantages and disadvantages of powder coating.

What is powder coating technology?

Electrostatic Power Coating Technology in English is also known as Electrostatic Power Coating Technology, invented by Dr. Erwin Gemmer in the early 1950s. After many years of development, electrostatic painting technology is now more and more optimized, helping to improve product quality and price a lot.

Powder coating is the process of coating a layer of plastic onto the surface of the parts that need to be covered. There are two common types of plastic used in powder coating: thermoplastic and thermosetting plastic.

There are two forms of powder coating: dry and wet:

• Dry electrostatic paint (powder paint): Is a form of direct powder spraying without mixing, applied to paint metal products such as iron, steel, aluminum, stainless steel…
• Wet electrostatic powder coating (using solvent): Powder is mixed with solvent or water, applied to paint products made of metal, wood plastic, etc.

However, nowadays, powder coating is more commonly used because of its covering efficiency and economy.

The powder coating formula used for electrostatic painting technology includes: Organic polymer compounds, curatives, pigments, leveling agents, and other additives. All are mixed together and melted to form a homogeneous mixture, then cooled and ground into a fine powder, called electrostatic powder coating.

Currently on the market there are 4 popular types of electrostatic powder coating: Gloss, Matt, Texture and Wrinkle used for both indoor and outdoor conditions.

Working principle of electrostatic painting technology

Electrostatic painting technology uses electronic principles to create adhesion for the paint film. The paint layer will be coated on the surface of the material with a special paint spray gun so that when the paint powder passes through the gun, it will be heated and charged positively (+) at the nozzle tip, then pass through the nozzle and move along the electric field to reach the negatively charged paint material (-). At this time, thanks to the attraction between the charged ions, the paint powder slowly adheres to the paint material. This method helps the paint powder to be evenly spread around the material, and can move to most hidden surfaces.

Advantages of powder coating

Do you know why powder coating technology is becoming more and more popular? That is because this painting technology has a series of outstanding advantages compared to other painting methods, not only is it economical but also environmentally friendly because it does not require the use of solvents like water-based paint.

1. Economic

In fact, during use, many people have realized that 99% of excess paint is completely reused (excess paint powder during the spraying process is recovered for reuse) and there is no need for primer, so powder coating technology helps save a lot of costs and construction time. In addition, the time to put the product into use is also shortened because when covered with the final layer of powder coating, the product only needs 20 minutes of maintenance to be ready for operation. Meanwhile, with conventional paints, it will take many days for the paint to dry and the product to adapt to the environment.

2. About usage characteristics

With its simple characteristics, we can use electrostatic paint very easily. The painting process can be easily automated (using an automatic gun spray system) which saves a lot of labor. Powder paint is also very easy to clean when it accidentally sticks to people or other equipment during the construction process without using any solvents like with water-based paint.

3. About quality

Powder coating technology is considered to create a coating layer twice as thick as other types of paint, so it often has a long-lasting finished product, high gloss, standard and rich colors. A good quality powder coating will be very durable, not corroded by chemicals or affected by chemical agents or weather for a long time.

4. Protective effect

The function of electrostatic paint is to prevent air and moisture from contacting the metal surface to limit oxidation and electrochemical corrosion of the painted object. The combination of pigments in the paint layers is not only for decorative purposes but also has the effect of protecting the metal. The effect of protecting the metal surface here comes from the ability to inhibit metal corrosive agents of the substances in the pigment. Inhibiting substances are often ions of metals such as Zn, Mg, Pb, Ni, Cr, Na, K, P…

5. High safety

The main components of electrostatic powder coating are resin, pigment and additives. Powder coating is a solid and does not evaporate easily in the air, so it does not affect health at all, unlike conventional paints that contain toxic solvents and volatile organic compounds. When painting, painters can completely avoid direct contact with powder coating by simple labor protection measures such as using masks, gloves, goggles, wearing long clothes, etc.

Since powder coating does not contain solvents or organic compounds, it does not harm the environment during application. Powder coating waste is classified as low-hazard and can be disposed of in landfills. Meanwhile, conventional paints contain toxic chemicals that have been shown to deplete ozone and create hazardous waste that requires special treatment.

Disadvantages of powder coating

Color Change: Since unused powder paint particles are collected and reused, there is a risk of mixing them together. This makes color matching inaccurate.

System construction costs: Electrostatic spraying requires a spray gun and an air compressor. In addition, a drying oven and a large power source are also needed to generate high voltage for the spray gun. This leads to high initial costs.

In addition, workers must have a lot of experience and know the painting process well to be able to work in the system. Therefore, businesses need to spend more on labor costs and worker training costs.

Powder coating process

As we mentioned above, electrostatic painting technology is very simple, it can be done without professional training. However, to ensure your safety and product quality, you need to ensure that you follow the 4-step electrostatic painting process below.

Step 1: Paint surface treatment

Surface treatment of paint helps ensure that the paint powder has better adhesion, beautiful color and higher durability. At this step, impurities on the surface of the painted material such as rust, grease, dirt and other organic impurities will be removed so that the material surface can better contact the paint. Normally, people will use the method of surface treatment with specialized chemicals contained in tank systems, including the following tanks:

• Degreasing tank.
• Rust removal tank.
• Clean water tank.
• Surface shaping tank.
• Surface phosphating tank.
• Product passivation tank.

The paint materials are separated by material, color and order, then put into stainless steel mesh and then dipped into surface treatment tanks. The time of soaking the product in the chemical tank will depend on the material of the paint material and the product must be lifted and lowered at least 2-3 times.

After surface treatment, the product will be put into the drying oven. Here, the paint material is dried at a maximum temperature of 120oC for 10-15 minutes to dry the moisture. The product after treatment must be kept in a dry, airy place, free from water and chemicals.

Step 2: Spray paint

The electrostatic painting process will take place in the paint booth. The paint booth not only ensures that the paint does not spread too much into the air, but more importantly, it helps to recover the excess paint powder for reuse in the next painting. There are 2 types of paint booths:

• Type for 1 spray gun (single spray booth): Using 1 spray gun, the painted object is hung and hooked by hand into the spray booth.
• Type for 2 spray guns (double spray booth, symmetrical spray booth): The painted object moves on the conveyor into the spray booth, 2 spray guns on 2 opposite sides spray on 2 sides of the product. To paint and collect powder paint, we need electrostatic spray equipment, and an air supply system including air compressor and moisture separator.

To carry out the electrostatic painting process, all products before being hung on the conveyor will be sprayed clean by an air compressor on the surface of the product. The direction of the dust spray must be facing outwards, not towards other people or into the paint room.

Before painting, you need to check all spraying equipment including paint gun, nozzle, electricity, steam, ground, spray booth exhaust fan, lighting… When painting, the paint gun (GUN) must always be perpendicular to the object to be painted, the distance from the paint gun to the object to be painted is about 10 – 15cm for hand spraying, 20 – 25cm for automatic spray guns. For manual spraying (hand spraying), you should paint the corners first, paint the flat surface later, paint the bottom first, paint the top later.

Applications of powder coating