The powder coating process: The basics
Powder coatings are one of the hardest working coatings in the industry. With applications ranging from consumer goods like fridges to hard-wearing machinery and pipelines, powder coating is a billion-dollar industry. Whether your substrate is metal, plastics, wood, or MDF, a powder coating will provide extreme durability with an attractive finish.
The powder coating process can be broken down into 3 basic steps:
- Substrate preparation/pre-treatment
- Powder application
As the name suggests, powder coating is applied to a substrate in a dry powder form. The most common method of application uses an electrostatic spray gun, which applies an electric charge to the powder. When sprayed at a grounded substrate, the powder will accelerate towards it and the electric attraction is what causes it to stick. The piece is then put into an oven for the powder to cure; the heat causes the powder to melt and chemically react, creating a uniform film which is tightly connected and resistant to breakdown. A powder coat can also be applied by dipping the substrate into a fluidized bed of aerated powder.
Top 5 reasons to choose powder coating
Powder coating is already a billions-of-dollars-a-year business, and is only getting bigger. Here are 5 reasons why:
- Durability: It is more resistant to chipping, scratching, fading, and wearing than liquid coatings.
- Appearance: Unlimited color and finish choice (including gloss, matt, iridescent, glitter, and candy)
- Cost efficiency: It is cheaper than liquid paint, and with minimal to no wastage. Plus it is very long-lasting, and has a short cure time.
- Flexibility: Suitable for a wide range of materials, and purposes.
- Environmentally friendly: Solvent-free, very low/zero VOC, and excess powder can be recovered and reused, so minimal waste.
Choose powder coating for protection – not just looks
While the range of finishes may be dazzling, the real advantage of powder coatings is their physical properties. It is highly resistant to physical damage through chipping, flaking, scratching or abrasion. It is also resistant to chemicals, corrosion and weather. When applied is does not drip or sag and is thicker than most paints, reducing the need for layers. It is also very low maintenance after application. These are just some of the reasons why powder coating is trusted across industries; it has been for long the go-to coating for electrical appliances and is becoming more and more used in the automotive industry, and even furniture manufacturing benefits from it. A powder coating consultant will give you the information and advice you need to make the right choice for your project.
The different powder coating chemistries – know what to choose
Powder coating can be divided into two broad categories: thermoset and thermoplastic. Knowing which powder coating to choose means knowing the difference between thermoset and thermoplastic powders, and then working out which powder chemistry you need.
1. Thermoplastic powder coating
Thermoplastic powder coating melts and flows when exposed to heat, but once it cools and sets it does not change in its chemical composition. They are composed of long chain moelcules to begin with. Thermoplastic coatings form a smoother finish than thermosetting and are commonly applied through the electrostatic spray and fluidized bed application methods. They are more flexible than thermoset and have a higher impact resistance.
2. Thermosetting powder coating
Thermosetting powder coatings also melts and flows when exposed to heat, but after they form a continuous film they form crosslinks, changing their chemical composition. The crosslinks take the shorter molecules of the thermosetting powder and knit them together. This makes thermosetting powder heat stable and they will not re-melt if exposed to further heat after curing. Because of this stability, the majority of powder coatings are thermosetting powders.
3. Choosing the powder coating resin
As well as having different curing methods, powder coatings are also made of different coating chemistries. Epoxy, polyester, and polyurethane are just three of the possibilities, and each is used for different applications depending on their strengths. Below are the main powder coating chemistries and their applications.
- ACRYLIC POWDER COATING
A thermosetting resin mostly used in the automotive industry to provide a chip-resistant, smooth clear coat for vehicles.
- EPOXY POWDER COATING
Epoxy resin powder coating is thermosetting, durable, corrosion resistant, chemical resistant, and they adhere well to metals, but they are let down in their weatherability. Epoxy resins are not UV stable and so exterior exposure can cause them to chalk and fade. Because of this they are mostly used for interior applications for protective purposes. Fusion bonded epoxy powder coating (FBE) is used to protect pipelines from corrosion.
- POLYESTER POWDER COATING
Polyester is the most common thermosetting resin type due to the broad range of applications to which it is suited, and because it is one of the cheaper options. It comes in TGIC (triglycidyl isocyanurate) and non-TGIC varieties. Polyester powder coating has good flexibility, durability mechanical resistance, and chemical resistance. Used for exterior applications. There are also Super Durable Polyesters which offer extended color and gloss lifespans.
- HYBRID EPOXY-POLYESTER POWDER COATING
An epoxy-polyester blend provides toughness, chemical resistance, color stability and excellent decorative appearance. They have better weatherability than pure epoxy, but decreased chemical and corrosion resistance.They are commonly used for office furniture, and not really suited for outside.
- FLUOROPOLYMER POWDER COATING
Thermoset fluoropolymer powder coating is typically used in exterior architectural applications as they have excellent weatherability, UV stability, and color and gloss retention. They are the longest-lasting outdoor powder coating option.
- NYLON POWDER COATING
Nylon powder coating is thermoplastic and finds use where friction reduction, resistance to corrosion and chemicals, and a cosmetic finish are required. Kids playground equipment, shopping carts and wire shelving use nylon coating.
- POLYURETHANE POWDER COATING
A thermosetting polyurethane resin is used for exterior applications with a need for hardness and a lower film build. They have excellent corrosion resistance and durability, but are more expensive than alternatives.
- SILICONE POWDER COATING
Used as heat resistant powder coating for temperatures up to 1000°F. For high heat applications such as engines or exhaust systems use silicone powder coating.
Get in touch with a powder coating specialist in the US
With powder coating being such a big business, it is no surprise that there are several companies and manufacturers operating in the US, including AkzoNobel, Valspar and Axalta. For a cost breakdown of powder coat treatments as well as equipment, visit our pricing page. For powder coating consultants, contractors and specialist applicators, please check out our regional guides:
If you require any additional information on powder coatings, consultants, contractors, equipment or manufacturers, do not hesitate to contact us. Our experts are here to help! Simply use the button below and tell us a little about your project to get the ball rolling -our quotation service is 100% free. In collaboration with our coating partners, we will connect you with the coating solution for your needs.