Powder coatings have become the finish of choice for a number of industries. Heavy equipment, marine products, electronics, other outdoor recreational products to appliances are all taking advantage of powder coating's performance . Key advantages that powder coatings have over liquid coatings include a solvent-free workplace, lower overall line costs and ease of cleanup. Powder coatings also can help finishers with their sustainability efforts, as they have zero to very low VOCs and offer over-spray recycling capabilities and product waste that can generally be disposed of in conventional landfills (applicable regulations should be checked for proper disposal methods).
Proper maintenance and spray techniques are essential to ensuring efficiency and effectiveness in any powder coating process. Falling into bad habits is easy and often goes unnoticed, but can result in efficiency losses and quality issues. And while supervisor bench marking of operations is a great best practice for keeping a line running as smoothly as the day it was first installed, even the most productive powder coating lines can experience issues.
Ten Steps for Success
1. Get The Right Charge
Most electrostatic sprayed powder coatings are given a negative charge out of the powder gun, while the part itself is grounded. This ground provides the opposite charge and attracts the powder to the part, but the part itself must be properly grounded for this to occur. A poor ground affects the transfer efficiency and results in improper film build. Proper maintenance practices can help to prevent this from occurring.
2. Control The Amount
The key to quality powder coating is to spray just the right amount of powder with the minimum amount of air necessary. Excessive feed air pressure and powder volume will not result in faster or better coated parts, and generally speaking, the finish, the spray guns and the booth may be compromised as a result.
3. Clear The Air
The importance of air quality to powder coating should not be underestimated. Many of the problems experienced in a powder coating spray installation can be directly traced to poor compressed air quality. Airborne moisture, oil and particulate matter such as dirt or dust have the greatest influence on air quality in the coating process.
4. Maintain The Correct Size Particle
One of the primary benefits inherent to powder coating is the ability to reclaim and reuse spray that does not adhere to parts. However, trying to coat with only reclaimed material is both inefficient and costly. Every powder coating is manufactured to a particular size range. That same range needs to be maintained to ensure proper coating thickness, finish quality and transfer efficiency — regardless of whether it is virgin or reclaimed powder.
5. Keep Colours Separate
Improper colour changeovers can lead to cross contamination that can, in turn, lead to rejected parts.
Changing colours provides the opportunity to not only clean the entire system but also to ensure that spray guns and components are set up and operating properly. With certain types of powder products, there is more of a risk of contamination hazard than with others, as they may be highly incompatible with other powder products. Two different powder coatings may be incompatible due to various formulation differences such as resins, texturing, additives or other raw materials included in the formulation. For that reason, it may be advisable to have dedicated hoses for specific colours and/or textures to avoid contamination issues.
6. Clean & Pretty
Coating quality will only be as good as the quality of the surface to which it is anchored. Poor pretreatment practices may create adhesion, corrosion resistance and impact resistance problems on coated parts. There are varying pretreatment technologies available to finishers.
7. You Get What You Pay For
All powder coatings are not the same. Purchasing only on price per pound and specific gravity is not a formula for real savings. Rather, it is better to understand the price per square foot covered, or the applied cost. Basing purchase decisions solely on price per pound and specific gravity ignores key performance and process standards, such as the coating’s durability, UV resistance, uniformity of particle size, or whether the powder coating contains fillers or off-specification resins.
8. Store Like A Antique Book
All powder coatings require a cool, dry storage environment. Ideal storage conditions are at temperatures below 80 degrees and humidity levels under 50 percent, and low-cure powder coatings may require even cooler temperatures. In locations prone to hot, humid conditions, air conditioned storage is a good option.
9. Curing - Three Types
There are really only three outcomes when it comes to curing the powder coating: the proper cure, under-curing, or over-curing, with temperature and time being the key variables in the process. It is important to note that the full performance properties of the coating are achieved only when the film is properly cured. Every powder coating has a set cure schedule of time and temperature as recommended by the supplier. Powder coating suppliers can recommend a solvent rub test method that can be used to determine full cure on-line.
10. Focus On Quality and Proactive Maintenance
Powder coating success is highly dependent on an organization’s commitment to produce quality parts. Developing and adhering to a well-thought-out process that includes proper coating techniques is fundamental to that commitment. But the influence that quality control and preventive maintenance practices have throughout the organization should not be underestimated.