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What is the difference between spray painting and powder coating

by: Dec 01,2023 267 Views 0 Comments Posted in Engineering Technical

powder coating spray painting sheet metal CNC machining

Spraying various coatings on the surface of the product is one of the most important surface treatment processes. It can not only make the product look good, but also protect the product matrix.

Among them, plastic spraying and spray painting are two widely used spraying processes. If there is any difference between them, I believe many people have not figured it out. Some even think that they are just different names for the same process. In fact, they are two different processes, using different equipment and processes.

In fact, whether it is powder coating or spray paint, they are both spray coatings. If you understand powder coating and spray paint respectively, you can know the difference between them.

Let’s look at the simpler spray paint first.

Spray paint

Spray painting is a simple and commonly used surface treatment process. It puts paint into a container, pressurizes it with machinery and equipment, and sprays the paint on the product in the form of mist to form a paint film. Widely used in ships, locomotives, bridges, machinery and other fields.

The main function of spray painting is to protect products or semi-finished products from rust and corrosion, and it can also play a decorative role to make the product look more beautiful.

Classification and characteristics of spray paint

According to the operation mode, spray painting can be divided into two types: manual spray painting and automatic spray painting.

Manual spray painting is when workers hold a spray gun and spray the product according to the shape of the workpiece.

The advantages are flexible and convenient operation, suitable for products of different environments, shapes, and sizes, simple equipment, and low energy consumption;

The disadvantages are low production efficiency, unstable spray quality, high labor intensity for workers, vulnerability to paint mist pollution, and poor working conditions.

Automatic spray painting uses a mechanically controlled spray gun to spray products.

The advantages are high productivity, stable spray quality, and good working conditions for workers.

The disadvantage is that the equipment is more expensive and the equipment structure is complex.

Spray painting can also be divided into two types: air spray painting and high-pressure airless spray painting.

Air spray painting uses a spray gun as a tool and relies on the airflow of compressed air to blow away the paint, atomize it, and spray it onto the surface of the product to form a paint film.

Air spray painting has the advantages of using simple equipment and forming a dense coating; however, air spray painting will also cause a large amount of paint mist to be generated during the spray painting process, polluting the air, causing large paint losses, and moisture and other impurities in the compressed air will easily Mixed into the paint flow, the treatment is not clean, which will affect the quality of the coating and other shortcomings.

Air spray painting is widely used in manual spray painting where the painting area is large and the workpiece has a complex shape. Since a large amount of paint mist is generated during the painting process, it is necessary to limit the pollution of the paint mist to the environment.

High-pressure airless spray painting uses a high-pressure pump in a closed container to pressurize the paint and spray it out from the spray gun. Due to the sudden drop in pressure, it immediately expands and atomizes violently, and sprays it onto the surface of the workpiece to form a paint film.

High-pressure airless spray painting has the advantages of high productivity, less paint mist, low air pollution, good working conditions and strong paint film adhesion. Moreover, since there is no water, oil and other impurities mixed in the paint flow, the coating is protected Regardless of its performance, high-pressure airless spray painting also has disadvantages such as more complex equipment structure, less uniform coating than air spray painting, and poor decorative properties.

High-pressure airless spray painting is suitable for spraying small products. In order to improve sanitary conditions, high-pressure airless spray painting operations should be carried out in the spray booth.

Spray painting process

The product must also be treated before painting. The surface of the product must be cleaned by rust removal, oil removal, etc., so that the paint layer will be stronger.

The surface of the processed product must be cleaned, and after natural drying, the product can be spray painted.

Spray painting can be done directly by spraying a layer of paint, or it can be sprayed 2-3 times repeatedly in order to obtain a dense and strong paint layer. In this way, the first spray paint is also called the primer, and it needs to be polished before the next spray paint.

Powder coating

Compared with spray painting, powder coating is more complicated. It is a process in which paint powder is directly sprayed on the product through equipment to play a protective and decorative role. Powder coating is also usually called electrostatic powder spraying.

Powder coating is a widely used metal surface treatment technology and is widely used in hardware, home decoration, building materials and other fields.

The principle of powder coating

During the spraying process, the powder coating contained in the container is sent to the spray gun port through compressed air, and high-voltage static electricity is generated at the front end of the spray gun port and an electrostatic field is formed.

When the paint powder passes through this electrostatic field, it will discharge them. Finally, each powder will become a charged paint ion. Under the action of electrostatic force, when it is sprayed out, it will be absorbed by products of opposite polarity. Attract, thereby adsorbing on the surface of the product.

When the coating powder accumulates more and more, the charge will also accumulate. When it reaches a certain thickness, the charged powder will be repelled by the charged powder covering the product, and the coating powder will no longer continue to accumulate.

Characteristics of powder coating

Plastic spraying can directly use coating powder, which does not need to be diluted with liquid, and is less harmful to the environment and human body.

The coating quality after using this kind of electrostatic spraying is very good, and the adhesion is also strong; the technical requirements for workers are also relatively low, the curing time is short, and there will be no liquid sagging and many other advantages.

However, plastic spraying also has disadvantages such as the surface being difficult to repair and the cost being high.

Powder coating process

Like other surface treatment processes, the product also needs to be treated before spraying to make the surface of the product clean before spraying.

In the plastic spraying process, the coating powder is sprayed directly on the product, and the adsorption force is not very strong at this time, so an important step is high-temperature curing.

By placing the product sprayed with paint into an oven at a certain temperature, under the action of high temperature, the paint powder will melt and level itself, and finally solidify to form a dense and strong spray layer.

The difference between spray painting and powder coating

By introducing powder coating and spray painting respectively, you can know the difference between them.

The leveling of spray paint is better than that of powder coating. This is because the molecular structure of the additives and solvents used in spray paint will help leveling, but these ingredients are not included in spray paint.

Spray paint can repair small areas, but powder coating cannot. Moreover, spray paint is more flexible than powder coating, so spray paint can be bent in small sizes.

Spray paint has rich decorative features, fast delivery time, and can be customized or produced in small batches.

Powder coating must be baked at high temperature, so the adhesion will be better, but there will also be requirements on the size of the product. It is too big to be put in the oven, while spray painting does not require size requirements on the product, and can be sprayed on a large area.

Therefore, one cannot say who is better than the other between spray painting and powder coating. Appropriate spraying processes need to be adopted according to different product requirements.

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