What Is an Electrostatic Sprayer?
An electrostatic sprayer is a device used for electrostatic spraying.
Electrostatic coating is a method in which paint particles and the target to be coated are electrically charged. It is considered more efficient than conventional coating and has the advantage of reducing the amount of paint used.
However, there are disadvantages, including the ease of paint adhesion depending on the shape of the coated area. When solvent-based paints are used, sparks may occur and cause ignition, necessitating measures to prevent ignition.
Uses of Electrostatic Sprayers
As mentioned earlier, electrostatic coating is a highly efficient method, reducing paint usage and operation time. It is particularly cost-effective for mass-produced products and is widely used in coating automobiles, building materials, home appliances, and other items.
To address the challenge of paint application depending on the shape of the coated area, technology has been introduced in the automotive coating industry that uses air to adapt the coating to the shape of the part being coated.
Principles of Electrostatic Sprayer
Electrostatic coating is based on the phenomenon of electrostatic attraction.
When the target to be coated is grounded, and the negative electrode of the electrostatic sprayer contacts it, a positive charge forms on the surface of the target. This phenomenon is known as electrostatic attraction.
As the voltage applied to the electrostatic sprayer increases, corona discharge occurs at the tip of the discharge electrode. This discharge ionizes the oxygen in the air, producing oxygen anions (ozone). These oxygen anions attach to the paint particles, rendering them negatively charged.
The ion current formed by the oxygen anions carries the negatively charged particles to the target. Upon reaching the target, the paint particles adhere to the positively charged target surface through electrostatic interaction. This is the fundamental principle of painting with electrostatic sprayers.
In electrostatic sprayer coating, the ease of paint adhesion depends on the concentration of ionic current. Therefore, convex areas with higher current concentration are easier to coat, while concave areas with lower concentration are more challenging to cover.
Disadvantages of Electrostatic Sprayers
While electrostatic coating is efficient for large quantities of uniform products, it has certain drawbacks:
Uneven Coating and Peculiar Defects: Due to the reliance on electrostatic forces, non-uniform shapes may result in uneven coatings, with paint accumulating more on convex surfaces, potentially leading to defects such as “dust and dirt spots” and “yuzu-tsuki” caused by excessive voltage.
Difficulty Achieving Thin Film Thickness: Electrostatic coating cannot produce thin films; the minimum thickness is about 30 μm. Attempts to achieve thinner coatings can result in unevenness.
Challenges in Small-Quantity, High-Variety Production: Electrostatic coating involves complex processes, from cleaning to coating and high-temperature baking. Specialized coating equipment and safety measures are required, leading to substantial initial investment costs.
Paint Powder Management: Handling paint powder requires safety measures against dust explosions, and powders are prone to oxidation and contamination.
Difference Between Electrostatic and Electrodeposition Coating
The main difference between electrostatic and electrodeposition coating lies in the application method. Electrostatic coating sprays paint and relies on electrostatic forces for adhesion. In contrast, electrodeposition coating immerses the object in a paint bath and uses electrolysis to deposit a uniform coating film due to immersion in liquid paint.