what is powder coating

What is Powder Coating?

Powder coating is a type of surface finishing that involves the application of electrostatically charged powder onto an object, commonly referred to as a substrate. Once coating is applied, the part gets cured at a certain time/temperature making the coating go from a powder state to a hardened protective layer.

This process is applicable to both metallic and nonmetallic surfaces. Generally, the process takes place automatically along a conveyor system.

Advantages of Powder Coating

·       No solvents

·       Protection and Decoration

·       Resistant surface

·       Close to 100% material utilization

·       Outstanding results in one coat

·       High mechanical resistance

·       Easy and clean application

·       Applicable on various substrates

What are Powder Coatings made of?

Powder coatings are dry mixtures, that generally consist of four main components:

Resins&Hardeners, Additives, Pigments, Fillers.

Resins & Hardeners

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.

·       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.

·       Polyurethane: Polyurethane resin excels in providing a smooth and glossy finish. You'll find it in high-quality automotive coatings and wood finishes.

·       Acrylic: Acrylic resin provides excellent color and gloss retention, making it a great choice for decorative and architectural applications.

·       Fluoropolymer: These resins are known for their extreme durability and resistance to chemicals and UV exposure. They're often used in applications where longevity is crucial.

·       Polyester TGIC Free: A variation of polyester resin, this choice is eco-friendly, with no TGIC (Triglycidyl Isocyanurate), making it safer for both application and the environment.

When considering these resins, factors like Glass Transition Temperature (Tg), reactivity, and melt viscosity come into play. Tg marks the temperature at which the resin transitions from a hard, glassy material to a softer, rubbery state. Reactivity tells us how quickly the powder coating formulation gels at a specific temperature, usually measured in seconds. Melt viscosity relates to the rate at which the formulation melts during the extrusion process, affecting its application.

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

Additives

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

·       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.

·       Anti-Static Additives: Improving the coating's electrical conductivity, these additives help it dissipate electrical charge to the ground.

·       Gloss Control Additives: Achieving the desired level of gloss can involve both chemical and physical methods. This helps control the coating's shine.

·       Special Effect Additives: For unique finishes, additives can create textured surfaces, or provide resistance to marring and slipping.

In essence, additives are versatile components, fine-tuning the powder coating to meet specific requirements and deliver exceptional results in diverse applications. So, the next time you see that flawless powder-coated finish on your favorite products, you'll know that it's the result of a perfectly balanced combination of these four essential ingredients.

Pigments

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.

Fillers

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.