Powder coating is one of the most durable finishes that can be applied to industrial manufactured products, and offers excellent corrosion protection and is very safe because of its lack of volatile organic compounds.

Powder coating is a multi-step surface finishing process employing two types of powder coatings, namely; Thermoplastic and Thermosetting, in which dry, free-flowing powder material is applied to a surface, melted, and hardened into an even coating. Thermoplastic powders melt and flow when heat is applied, but they continue to have the same chemical composition once they cool and solidify. Thermosetting powder coatings also melt when exposed to heat, but they then chemically cross-link within themselves or with other reactive components. The cured coating has a different chemical structure than the basic resin.

Thermosetting coatings are heat-stable and, unlike thermoplastic powders, will not soften back to the liquid phase when reheated. Thermoset powders can also be applied by spray application to develop thinner films with better appearance than some thermoplastic powder coatings.

Powder coating is based on polymer resin combined with pigments, curative, flow modifiers, leveling agents, and several other additives. All ingredients are melt mixed together, then cooled and ground into a powder. Preheating achieves a uniform finish, and cooling helps form a hard coating. Powder coating utilizes a Spray Gun, Spray Booth and Curing Oven.

This finishing process is suitable for various materials, including metals, plastics, glass, and Medium Density Fiberboard and can provide both functional and decorative surface coatings in a wide range of colors, finishes, and textures that are not readily achievable by conventional liquid coating methods.

During the powder coating process, the powder is applied to a substrate’s pretreated surface, melted, and then dried and hardened into a protective/decorative coating. There are three stages to this process:

1. Surface preparation
2. Coating application
3. Heat curing

For the coating process to run smoothly and at optimum capacity, manufacturers and finishing service providers should consider several factors, such as the substrate material being coated and its properties, as well as the type of powder coating material employed.

Surface preparation

This process involves removal of oil, soil, lubrication greases, metal oxides (rust), welding scales etc. This is essential prior to the powder coating process. It can be done by a variety of chemical and mechanical methods. The selection of the method depends on the size and the material of the part to be powder coated, the type of soil to be removed and the performance requirement of the finished product.

Coating Application

There are two types of powder coating materials that can be applied. The type of coating material being used in a coating application, in part, determines the application method. There are two main methods of powder coating employed by manufacturers and finishing service providers- electrostatic deposition (ESD) and fluidized bed powder coating. We, at Al Amanah Metal Coating, use ESD method.

Electrostatic Deposition (ESD): For most metal parts being powder coated, the coating material is applied via electrostatic spray deposition. This application method employs a powder spray booth, powder feeder, electrostatic spray gun, with power units.

Heat Curing

The particularities and characteristics of the powder coating process’s curing stage are mainly determined by the method in which the powder coating is applied, as well as the type of powder coating material employed.

Curing ESD coated parts: Parts that are powder coated via ESD must be cured in a powder curing oven. While the cure schedule—the temperature and time that a powder coating must endure in a curing oven to achieve a full cure—for a powder coated part is mostly dependent on its size, shape, and thickness.

Generally a curing oven operating between 200°C and 230°C will result in cure times that range between 15 minutes and over 45 minutes. Accordingly, smaller powder coated parts require less curing time and lower volumes of heated air to cure fully, and larger parts need more. As the ESD coated part reaches the optimum curing temperature within the oven, the powder particles melt and flow together to form a continuous film over the part’s surface.

Once the powder coated part is cool enough to handle, the part can be assembled, packaged, and shipped.