Regardless of the industry, they’re used in – whether auto, aircraft, appliance assembly, or other – reactive metal parts need to be adequately finished for several reasons. It’s not only about the decorative finishes; a surface coating is essential for protecting the metal from corrosion. Colorful metal parts aren’t just for show – these surface finishes ensure that the metal (such as iron or carbon steel) won’t react with oxygen and form rust.
There are two primary methods for finishing metal – wet painting and powder coating. Both have their pros and cons, but the industry has been leaning towards powder for quite some time now.
Let’s answer the question of why powder coating is better than liquid painting.
Chemistry and Application
The chemistry of these two coatings is simple – wet paint is liquid and contains a solvent, while powder is dry and doesn’t have any solvent. Both come with different pigments, additives, and resins. Any differences in their application, texture, color matching, and more come from this fundamental fact that wet paint is a suspended liquid, and powder is exactly what its name says: dry powder.
As for the application of the coatings – there are some minor differences.
The pretreatment phase is the same. Before using either coating method, the metal surface needs to be spotless – free of any moisture, oil, dirt, or other types of contaminants. Any of these will interfere with surface adhesion and lead to a poor paint job.
Once the pretreatment is complete, the coating process is slightly different for each coating option.
- Powder Coating
The two most common ways of applying powder coating are electrostatic deposition (ESD) and fluidized bed powder coating.
The essence of ESD is that dry powder coating material is shot through a gun to the metal surface in an electrostatic spray. This electrostatic process means that the powder particles are charged with electrostatic energy. The electrically-charged particles are attracted to the metal’s electrically grounded surface and adhere to it.
On the other hand, the fluidized bed powder coating includes preheated metal parts dipped into powder suspended within a fluidized bed.
For the powder color to dry, it needs to be cured in a special curing oven at temperatures over 400F. Once the coating sets, you will have a thick and shiny surface coat.
A sound powder coating system includes a powder spray booth, an electrostatic spray gun, a powder feeder, and potentially a power unit.
- Liquid Coating
Liquid coatings require different types of spray guns to propel the paint’s atoms towards the surface you want to paint.
Some examples of spray gun technologies used in the liquid painting are high-volume, low-pressure (HVLP) guns, airless spray guns, and electrostatic-based guns similar to those that apply powder.
The significant difference in this process is that wet paint typically air dries. If a manufacturer wants to speed up drying times, they can use curing ovens with temperatures between 130 and 170F.
Is powder coating truly better?
The debate seems to be endless – why is powder coating better than liquid painting? Is it more durable? Is it less expensive? Why do so many experts recommend powder coating over wet paint?
The answer to these questions lies in several criteria we can examine.
- Cost Efficiency
At first, it may seem illogical that powder coating is more cost-efficient, considering the high upfront costs it mandates. Powder coating equipment and materials are more expensive and not as readily available as those for wet painting.
However, the reduction of costs you will experience quickly after switching to powder coating will be worth it.
The powder can be collected and reused. It is estimated that over 70% of liquid paint is lost during the application phase due to overspray. In comparison, less than 5% of material is lost to powder coating overspray.
Another reduction in costs is achieved through lower labor costs. Almost anyone can do powder coating, and you can even automate it. You don’t have to rely on highly trained operators to apply it, like with liquid coating.
Lastly, powder costs less to be disposed of. It has a high utilization rate, and any amount that has to be disposed of at the end of the day isn’t subject to the same restrictive environmental controls as conventional paint is.
- Performance
Aside from providing a specific look, finishing layers also ensure corrosion resistance and protection against environmental damage. If there is any scratching or chipping, the protective barrier loses its function and is less effective.
The powder is physically much tougher than liquid paint. Because of the curing step in the powder coating process and because it can be applied as a thicker coating, it is resistant to chipping, scratching, and other types of wear. This is why powder coating is ideal for any outdoor metal product, such as bike racks or metal posts.
Furthermore, a powder coating finish retains its color for longer than wet paint. A coated surface can be exposed to direct sunlight, moisture, and heat, which will slowly break down the resin components of paint and powder coatings. This is known as chalking, and polyester-based powder finishes are exceptionally resistant to chalking.
- Health and Safety
Another advantage of powder coating over liquid paint is that it is safer to store and apply.
Conventional liquid paint poses a hazard for various reasons. It is highly flammable, meaning that careless storage can easily lead to a chemical fire.
Wet paint is also a health risk for the operators applying it. It contains a range of volatile organic compounds (VOCs). Volatile means that they evaporate into the air and can be breathed in. People working with liquid paint – especially in enclosed spaces – can suffer from respiratory problems and other compounding illnesses.
VOCs are also an environmental problem, not only a health one. They are a significant source of industrial pollution.
In contrast, the powder doesn’t contain any fluids that can evaporate or any VOCs, and thus it doesn’t pose the same health and safety risks as traditional liquid paint. When working with powder, operators only have to wear a dust mask and nothing else.
Conclusion
The two main reasons for finishing metal surfaces with a layer of paint are their style or appearance and protection against rust and environmental damage. A previously prepped, smooth surface can be treated with wet paint or a dry powder coating. Both types of finishes have similar application processes that involve spray painting.
However, these two coatings don’t have the same characteristics. Powder takes the top spot over liquid paint coating because it is more durable, more cost-effective, and immeasurably safer both for the workers and the environment.
The cost-effective part – powder coating equipment may cost more initially, but the savings over the following time period make up for that starting investment. Excess powder can be collected again and reused, and labor costs will also be reduced.
Performance-wise, there is nothing to worry about with a powder coat. It is more durable than traditional paint; the color doesn’t fade as much over time, and it is resistant to chipping, chalking, scratching, and other forms of damage. The most resistant forms are polyester-based powders. If you need a custom finishing system for your business, GAT systems can provide that for you. Contact us if you have any questions about the powder vs. wet paint topic or would like to know how you can use the benefits of powder to the advantage of your business.
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