Applying various coatings to the surface of a product is one of the most important surface treatment processes, which not only enhances the appearance of the product but also protects its substrate. Among them, spray painting and powder coating are two widely used spraying techniques, which have differences in equipment and process flow. This article will provide a detailed introduction to the differences between these two processes.
Spray painting is a simple and widely used surface treatment process. Paint is placed in a container and then pressurized with a machine before being sprayed onto the product in a mist-like form to form a layer of paint film. Spray painting is widely used in fields such as ships, locomotives, bridges, and machinery. It can protect products or semi-finished products by preventing them from rusting or corrosion, and make products look more attractive.
According to the method of operation, spray painting can be divided into two types: manual spray painting and automatic spray painting.
Workers hold the spray gun to spray the product according to its shape.
Advantages: flexible operation; suitable for products of different environments, shapes, and sizes; easy-used equipment; low energy consumption.
Disadvantages: low production efficiency; unstable spraying quality; high labor intensity for workers; easily affected by paint mist pollution.
Using machinery to manipulate the spray gun to spray the product.
Advantages: high productivity; stable spraying quality; good working conditions for workers;
Disadvantages: high-cost equipment with complex structure.
Spray painting can also be divided into two types: air spray painting and high-pressure airless spray painting.
Uses a spray gun as a tool, and the compressed airflow blows the paint into a mist, which is sprayed onto the product surface to form a coating.
Advantages: easy-used equipment; good coating density;
Disadvantages: a large amount of paint mist is generated during the process, which is prone to air pollution; the loss of paint is large; moisture and other impurities in the air are easily mixed into the paint flow, which may affect the quality of the coating;
Air spray painting is widely used in manual spray painting where the painting area is large and the workpiece shape is complex.
Uses a high-pressure pump in a sealed container to pressurize the paint, which is then sprayed out of the spray gun, and then rapidly expands and atomizes due to the sudden pressure drop, forming a coating on the surface of the workpiece.
Advantages: high productivity; low air pollution; good working conditions; strong adhesion of the coating; as there are no moisture, oil, or other impurities mixed in the paint flow, the protective performance of the coating is also good;
Disadvantages: complex equipment structure; the coating is not as uniform as air spray painting; poor decorative effect.
High-pressure airless spray painting is suitable for small-scale product painting, and in order to improve hygiene conditions, the operation of high-pressure airless spray painting should be carried out in a spray booth.
The process of spray painting includes several steps. Before spray painting, the product's surface needs to be cleaned and treated to remove rust and oil, so that the paint layer can adhere better. After the treatment, the surface is washed and left to dry naturally before painting. There are two types of painting methods: direct painting with one layer of paint, or repeating the process 2-3 times to achieve a dense and sturdy paint layer. The first layer of paint is called the primer, and it needs to be sanded before the next layer of paint is applied.
Compared to spray painting, powder coating is more complex. It is a process of directly spraying coating powder onto a product through equipment to achieve both protective and decorative effects. Spray coating is also commonly referred to as electrostatic powder coating. It is a widely used metal surface treatment technology that has applications in hardware, home decoration, building materials, and other industries.
During the process of powder coating, the material contained in a container is sent to the spray gun through compressed air. At the front end of the spray gun, a high voltage static electricity is generated, forming an electrostatic field. When the material passes through this electrostatic field, it will discharge and each powder particle will become a charged coating ion. Under the action of static electricity, the charged powder coating particles are attracted to the product surface with opposite polarity when they are sprayed out. As the material accumulates more and more, the charges will also accumulate. When it reaches a certain thickness, the charged powder particles will be repelled by the charged particles already covering the product surface, and the powder coating will not continue to accumulate.
Spray coating can directly use powder coating without the need for liquid dilution, which has less impact on the environment and human health.
Advantages: good coating quality; strong adhesion; low technical requirements for workers; short curing time; no liquid sagging;
Disadvantages: the surface is not easy to repair; higher cost.
Like other surface treatment processes, the product needs to be treated before powder coating. The product surface needs to be cleaned before spraying because the adhesion at this time is not very strong. Therefore, there is an important step, which is high-temperature curing: the product with the sprayed coating is put into an oven at a certain temperature. Under the effect of high temperature, the coating powder melts, self-levels, and finally solidifies to form a dense and strong spray layer.
Therefore, it cannot be said which is better between spray painting and powder coating, and the appropriate spraying process should be chosen according to the different product requirements.
Note: Pictures come from the Internet.
