What is powder coating?

Powder coating is a surface treatment that sprays plastic powder onto parts. Powder coating is also known as electrostatic powder coating. Its treatment process is a common metal surface treatment decoration technology used internationally.

Principle

Its working principle is to charge the plastic powder through high-voltage electrostatic equipment, and spray the coating onto the surface of the workpiece under the action of the electric field. Powder coating is fed into the spray gun by the powder supply system with the help of compressed air. A high-voltage electrostatic generator is applied to the front end of the spray gun to generate high voltage. Due to corona discharge, dense electric charges are generated near it. When the powder is sprayed from the nozzle, charged coating particles are formed. Under the action of electrostatic force, they are attracted to the workpiece with opposite polarity. As the amount of powder sprayed increases, the charge accumulates more. When it reaches a certain thickness, it stops being adsorbed due to electrostatic repulsion, so that the entire workpiece obtains a certain thickness of powder coating. The powder is then heated to melt level and solidify, forming a hard coating film on the surface of the workpiece.

Process

1. Pretreatment

This is a critical, foundational step to ensure the quality of the final coating. Its purpose is to remove impurities such as oil, rust, and dust from the workpiece surface and form a conversion film that enhances coating adhesion.
Typical process: Degreasing → Water washing → Surface conditioning → Phosphating → Water washing → Deionized water washing → Drying.
The pretreated workpiece must be completely clean and dry.

2. Electrostatic spraying

This is the core step. Powder coating is delivered to the electrostatic spray gun via compressed air from a powder supply system.
The spray gun tip is equipped with a high-voltage electrostatic generator that imparts a negative charge (typically 30-90 kV) to the powder particles.
The workpiece to be sprayed is grounded via a hanger, forming a positive electrode.
Based on the principle of electrostatic attraction, the negatively charged powder particles are evenly attracted to the grounded work surface. Even the backside and recessed areas of the workpiece are attracted to the powder through the "encircling effect," achieving complete coverage.

3. High-Temperature Curing

The sprayed workpiece is then heated in a curing oven.
The heating temperature is typically 180-200°C, and the curing time is typically 10-30 minutes, depending on the material and thickness.
During this process, the powder particles melt, level, and undergo a cross-linking chemical reaction. Upon cooling, a dense, smooth, and strong solid protective film is formed. This process is also called "plasticization" or "leveling curing."

Advantage

1. Excellent Protective Performance

High Corrosion Resistance: Powder coatings form a dense, cured coating that is free of the "pinholes" and "sagging" defects common with liquid paint. They effectively shield metal, such as steel and aluminum from air, moisture, and acids and base. For example, spray coatings for outdoor guardrails and automotive chassis components can significantly extend the rust protection period.
Excellent Abrasion and Impact Resistance: The powder coating thickness is controllable (typically 50-150μm, with some applications reaching 300μm). After curing, the coating is hard, providing excellent scratch and impact resistance. For example, after spraying, appliance housing and tool handles are less susceptible to scratches and paint peeling during daily use, significantly extending their service life.

2. Diverse Appearance

Diverse and Uniform Colors: Powder coatings offer a wide range of color options customizable Pantone color palettes are available, and the electrostatic spraying process ensures a uniform coating thickness. This eliminates color variations and creates a smooth, rich visual effect, making it particularly suitable for mass-produced, standardized products. A wide range of texture options: In addition to standard "gloss, matte, and semi-matte" finishes, special textures can be achieved through powder formulation adjustments, such as:
Textures: Sand, hammer, and orange, conceal minor substrate imperfections and provide a non-slip feel;
Functional: Metallic (containing aluminum powder and pearlescent powder to simulate a metallic luster), Antimicrobial (added with antimicrobial agents, used in medical devices and food processing), and Insulating (used in electrical components).
Strong coating adhesion: The powder adheres tightly to the substrate through electrostatic adsorption and high-temperature curing. Adhesion tests (cross-hatch method) typically achieve a grade of 0 (the highest grade, with no coating flaking), far superior to some liquid paints, which can easily flake due to thermal cycling or impact.

Environmental Protection and Safety: Low Pollution, No Hazardous Substances

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