Machinery Manufacture, Material

Electrostatic paint: Definition, application, classification

Posted on by Hà Kỳ Anh

Definition

Electrostatic painting uses electricity to improve paint sticking to metal surfaces. It works best with metals that conduct electricity like iron and steel.

The process involves giving the paint particles a positive charge and the metal a negative charge. When painting, the opposite charges attract and bond, creating a uniform and strong paint layer.

This results in a higher quality paint job compared to traditional manual methods.

Applications

  • Window frame
  • Table
  • Shelf, cabinet
  • Kitchen shelf
  • Balcony frame
  • Gate, fence
  • Production line, machinery
  • ……………

Classification

Electrostatic paint

Traditional/Water paint
  • A smooth, evenly painted layer with good adhesion
  • High gloss level
  • When touching the metal surface, the paint layer will appear firm and not smudged by hand.
  • The paint is uneven, with thick and thin spots, resulting in an unattractive paint color.
  • Low gloss level
  • When touching the metal surface, the paint layer will appear rough and slightly dull.

 

Advantages

  • Good adhesion, evenly covers the metal surface
  • Coat does not peel or flake after long term use
  • Resistant to oxidative chemicals, protects metal surface and increases product lifespan and shine
  • Wide range of colors, durable, beautiful, and high gloss for high aesthetic value, no negative impact on health and brings comfort during use
  • High durability increases the product’s lifespan, contributing to environmental protection
  • Easy to clean the product
  • Saves labor costs
  • Can be recycled

Classification

There are two forms of electrostatic paint: dry and wet. Dry electrostatic paint (powder coating) is a widely used painting technology because it has many advantages over wet electrostatic paint (using solvents) and traditional painting methods.

Painting process

For any electrostatic painting system, from manual to fully automatic, it must go through the following four processes:

Step 1. Surface treatment

The purpose of surface treatment is to help the product surface meet the following criteria:

  • Clean oil and grease (generated during machining and casting)
  • Clean rust, dirt, impurities… (usually generated during storage and transportation)
  • Clean the old paint layer for repainting
  • Prevent rust from reoccurring while waiting for painting
  • Create a good adhesion layer for the paint, increasing the resistance to bending and impact.

Chemical and mechanical (sandblasting) methods can be used to perform this process. The choice of method depends on the size, material properties, type of contaminants to be removed, and surface to be treated.

Different products may require different surface treatment methods to save cost, protect the environment, and maintain health. However, for automatic and semi-automatic painting systems, chemical surface treatment is often used.

Step 2: Drying After surface treatment, the product may still be wet and must be dried to ensure the paint layer quality. This can be done by:

  • exposing to sunlight
  • using a fan to blow air
  • drying in an oven (manual or automatic)

Step 2. Surface Drying

After surface treatment, the product may still be wet and must be dried to ensure the paint layer quality. This can be done by:

  • exposing to sunlight
  • using a fan to blow air
  • drying in an oven (manual or automatic)

Step 3. Powder Coating

Purpose of powder coating:

  • To create a high-adhesion powder layer
  • To evenly coat all surface crevices of the product

Execution:

An electrostatic spray gun applies positive electrical charge to the powder coating, which is then sprayed onto the negatively charged product surface. The opposing electrical charges cause the powder to strongly adhere to the product.

To carry out this process, we need:

  • A specialized electrostatic spray gun for powder coating
  • A spray booth to ensure proper coating standards, prevent powder from spreading into the environment, and make it easier to recycle excess powder. There are two types of spray booths:
    • Single booth: objects are hung in the booth and coated with one spray gun
    • Double or symmetrical booth: products move on a conveyor belt, coated by two spray guns with a powder recovery system.

Step 4. Drying the Paint

After the paint powder is sprayed, the product is taken for drying in the paint dryer.

The paint powder will melt at around 150°C and is kept at 200°C for a minimum of 10-15 minutes. The exact temperature and time depend on the properties of the material and the requirements of the paint powder manufacturer.

The aim of this step is to:

  • Form a paint layer with high durability and adhesion
  • Achieve the desired color and surface effect as specified by the paint powder manufacturer

Currently, there are 3 main production lines that manufacturing plants use for electrostatic or manual application, including automatic electrostatic, automatic spray and manual. Among these, the automatic electrostatic spray system is the most popular.

See more

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