Powder Coating: Everything you need to know

Think of resin and hardener as the base duo of powder coatings. They are responsible for the coating's foundational structure and performance. Here are some common resin chemistries:

• Polyester: Known for its excellent exterior durability, polyester resin is often used for applications where exposure to the elements is a concern, like outdoor furniture or architectural elements.
   
• Epoxy: Epoxy resin offers outstanding mechanical properties and corrosion resistance. It's commonly found in industrial and automotive coatings where durability is essential.
   
• Polyurethane: Polyurethane resin excels in providing a smooth and glossy finish. You'll find it in high-quality automotive coatings and wood finishes.
   
• Epoxy-Polyester (Hybrid): This is a versatile option that combines the strengths of both epoxy and polyester resins, making it suitable for a wide range of applications.
   
• Acrylic: Acrylic resin provides excellent color and gloss retention, making it a great choice for decorative and architectural applications.

These resins are important ingredients that provide powder coatings with crucial properties like mechanical strength, chemical resistance, exterior durability, and corrosion resistance.

Additives are, as the name suggests, ingredients that give a powder coating its unique characteristics and performance enhancements. They come in various categories. Some of those are for example:

• Appearance (Flow Control) Additives: These additives prevent issues like cratering or orange peel, ensuring a smooth and even finish.
   
• Degassing Additives: They help release air from the film while maintaining its open structure.
   
• Exterior Durability Additives: Including UV absorbers, these additives protect the coating from the harmful effects of sunlight and other environmental factors.
   
• Corrosion Resistance Additives: For coatings that need extra protection against corrosion, zinc dust additives come to the rescue.
   
• Charge Control Additives: They enhance the coating's ability to accept an electric charge during application.
   
• Gloss Control Additives: Achieving the desired level of gloss can involve both chemical and physical methods. This helps control the coating's shine.

Pigments bring life and color to the powder coating film. They can be organic or inorganic and play a primary role in defining the coating's aesthetic appeal. Considerations for pigments include their thermal stability at curing temperatures and their resistance to exposure conditions, such as sunlight.

Pigments provide two primary properties:

• Hiding Power: This determines how effectively the coating conceals the substrate's color or imperfections beneath it.
• Appearance: Pigments are key in creating the desired look and finish of the coating, from high gloss to matte.

These substances give the powder volume and, thanks to their particle size, ensure optimum packing density (ratio between pigments, fillers and binders). Natural minerals such as calcium carbonate are being used as fillers.

1. Pre-treatment: The substrate is freed from dust, scale, rust, grease, dirt and any oxide layers (for example on aluminum). There exist chemical and mechanical pre-treatment processes. In order to increase the corrosion protection and improve the adhesion of the powder coating a conversion layer is created on the piece during the pre-treatment. Following this the workpiece must dry completely.

2. Application of the Powder Coating: By using a powder spray gun, the powder coating is applied to the grounded surface. It is essential to avoid the entry of dust and dirt at this step. The powder spray gun creates a charged cloud of powder. As a result, the paint particles adhere electrostatically to the piece and form a layer.

3. Curing: The powder coating is then cured in an oven at temperatures between 110 and 250 °C. Various factors such as heating time and substrate thickness affect the final curing time.