Understanding powder coating: answers to the top 10 most common ...

Powder coating has become a go-to solution across numerous industries for delivering high-performance, long-lasting finishes. From fencing and automotive parts to urban and water infrastructure (and so many other things in between), it offers durability, aesthetics, and environmental benefits that make it a preferred choice over traditional liquid paints. But with growing popularity comes curiosity – many people have questions about how it works, where it can be applied, and what makes it so effective. So, let’s get started with answering the top 10 most frequently asked questions about powder coating!

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1. What is powder coating?

Powder coating is a dry finishing process where a mixture of finely ground particles is electrostatically applied to a prepared surface, typically metal. Once applied, the object is cured in an oven, allowing the powder to melt and form a smooth, durable, and environmentally friendly finish. This coating is highly resistant to corrosion, chemicals, UV exposure, and general wear and tear.

2. What materials can be powder coated?

Powder coating is most commonly applied to metals such as steel, aluminium, stainless and galvanised steel. However, advancements in technology have made it possible to coat some heat-resistant non-metal materials, including MDF (medium-density fibreboard) and certain plastics.

3. How does powder coating compare to traditional paint?

Compared to traditional wet paint, powder coating offers improved durability and a more uniform finish. There are no drips or runs, and it’s more environmentally friendly as it contains no solvents or volatile organic compounds (VOCs). Additionally, any excess powder can often be reclaimed and reused, resulting in less waste.

4. Is powder coating environmentally friendly?

Yes, powder coating is one of the most eco-friendly finishing solutions available. It produces zero or minimal VOC emissions and contains no hazardous solvents.

5. How long does powder coating last?

A properly applied powder coating can last upwards of 10 to 20 years, depending on environmental conditions. For outdoor applications, UV-resistant formulations help maintain the coating’s gloss and colour retention. Powder coating can even outlast traditional wet paint.

6. Can powder coating be removed?

Yes, powder coating can be removed through methods such as:

• Chemical stripping (solvents like methylene chloride)
• Abrasive blasting (other forms of media blasting)
• Thermal stripping (burn-off ovens)

7. Is powder coating suitable for high-temperature applications?

Certain high-temperature powder coatings are specifically designed for extreme environments, such as automotive exhaust systems, industrial equipment, and aerospace components. Some coatings can withstand temperatures from 600°F (316°C) to as high as °F (538°C), and in rare cases even higher.

8. How should powder coating powders be stored?

To maintain quality and performance, powder coating powders should be stored in a cool, dry environment away from direct sunlight and moisture.

9. Can powder coating prevent rust?

Yes, powder coating creates a sealed protective barrier that delays moisture and oxygen from reaching the metal surface, significantly reducing the risk of rust and corrosion. It helps prolong the lifespan of metal components, especially in harsh or outdoor environments where exposure to the elements is constant.

Due to its ability to resist rust so effectively, powder coating is widely used on items such as fencing, railings, car parts, machinery, and structural steelwork. When applied properly and maintained, powder-coated finishes can maintain their integrity for decades, making them a reliable and cost-effective choice for corrosion prevention.

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10. How can I ensure full powder coverage in difficult areas?

At Northpoint, we ensure that all of our projects are properly and evenly coated by using techniques such as adjusting electrostatic settings, preheating the part, using a deflector nozzle, or applying a conductive primer.

Powder coating is a versatile, durable, and eco-friendly finishing process that offers superior protection compared to traditional paint. Whether you’re looking to coat industrial equipment, automotive parts, or architectural structures, powder coating provides a long-lasting, high-quality finish.

You have questions, we have answers. In each issue of PCT, our extensive network of powder coating experts provides information to help you with your powder coating challenges. Let us know what’s keeping you up at night and we’ll do our best to help you get a good night’s sleep!

In a Jam
Q: I have a powder coating line and am experiencing problems with the grounding of my parts. Specifically, the problem is with the load bars on my conveyors. Is there a particular hook material or finish that is required for a good ground? We are currently considering removing our load bars to have them sand blasted. Is this a good solution? Looking for advice to get us out of our jam.

A:First, you are addressing one of the most important components for achieving a quality finish on your products in checking your ground. For both meeting the safety standards and obtaining the best transfer efficiency, all parts should be grounded and verified with a Megohmmeter. You should have less than 1 meg-ohm of resistance. It is best to start at the lowest part on your hanger and check each part, moving up the rack or hooks. You might be good near the top, but all it takes is one hanger or part to be covered with cured powder to prevent a proper ground. Normally, standard mild steel without any coating on it is used for load bars to provide the best electroconductivity for your ground. In your case, it appears that you have identified the issue as being with your load bars. To achieve a better ground, you are on the right track having the load bars blasted or chemically stripped. However, you should consider further investigation into “why” this is happening. It might be that your parts being coated are too close to the load bar and causing the load bars to be coated during the powder coating process. If this is the case, look into using longer hangers to get them further away from the powder cloud. You might also double check the air flow in your booth including cross draft and through the roof slot. The booth might be out of balance or need more air flow (typically 100 to 120 fpm) through your openings.

A: Yes, although this can be a touchy situation if the specifications are not clear for everyone in the supply chain. Powder coating characteristics generally fall into three categories: • Surface appearance such as color & gloss. • Physical properties such as texture or smoothness. • Environmental durability such as outdoor UV requirements or salt spray corrosion resistance requirements. These characteristics should be defined by you to meet the desired requirements. These can be given to the custom coater and their suppliers. With a clear definition, it should stop any finger pointing as all would understand what specification/ characteristic is required. The following are some tests that can be used to set the characteristics:
• Gloss: using a Glossmeter as in ASTM D523.
• Color: using a Colorimeter as in ASTM D.
• Smoothness: PCI Smoothness Standards as defined in PCI Technical Brief #20.
• Distinctness of Image: either visual observation or meter as in ASTM D.
• Contrast Ratio: for special substrates or reflectance instruments as in ASTM D or PCI Technical Brief #3.

Other physical characteristics that may be considered are film thickness, impact resistance, flexibility, adhesion, hardness, abrasion resistance, edge coverage, chip resistance, and post machining (drilling and tapping). Some environmental characteristics to consider are solvent resistance, stain and chemical resistance, humidity resistance, salt spray resistance as per ASTM B523, weathering UV resistance as per ASTM D822, and temperature resistance. One method would be to take a sample product that meets your requirements and send it to a lab to have the characteristics measured and documented which can then be used to set your standards. Another way would be to work with a powder producer to discuss and set these standards. One thing to remember, the tighter the standard and more characteristics that are required can increase the cost of the material and manufacturing of the product. You should keep the specification to what is needed for your product.

The Flame
Q: I am new to powder coating and serve as our company’s health and safety manager. I was trying to find information on the flammability and combustibility of powder coating in addition to what is on the material safety data sheets (MSDS). Would you be able to point me to where I can find such information?

A: As each powder coating is a unique formulation and has its individual characteristics, the MSDS would be the best place to find this information for any particular powder. However, if you are looking for some general information on powder coating flammability and combustibility you can refer to the National Fire Protection Association’s NFPA® 33 Standard for Spray Application Using Flammable or Combustible Materials. Specifically, the following chapters:
• Chapter 15—Powder Coating.
• Annex A—Explanatory Material.
• Annex C—Determining Ventilation Airflow for Powder Application Systems.
• Annex D—Fire Record. Your best bet would be to start in the Annex C section which covers determining ventilation airflow for powder application systems. It has great explanations as well as calculations and representative test data for various types of powder.

Real World Results
Q: We have been manufacturing our product for many years and I am looking to improve our coating performance. Our product is used outdoors, and our mission is to provide top quality performance for our customers. We need to know if there are any guidelines to correlate impact test results with real world performance. For example: XX foot-pounds would equate to a ¼ inch hail or YY foot-pounds is considered “tough,” etc.? Can you help me understand the correlation or point me to some testing that has been completed?

A: There is not a true correlation between impact testing and hail. However, standard durable polyesters can easily achieve 160/160 inch-pounds (direct/indirect on a Gardner impact tester) of impact performance but have limited weathering performance. Superdurable polyesters can achieve 120/120 inch-pounds of impact performance and have significantly improved weathering performance. Not all superdurables will have this; most superdurable polyesters have significantly reduced impact performance. You need to check the technical data sheet (TDS) to determine if a particular superdurable has what you are looking for or contact a powder coating manufacturer for advice.

Clean Enough
Q: We manufacture parts that are primarily cast iron and machined for use in the automotive, agricultural, and construction equipment (ACE) industries. We are not sure if we are cleaning our parts properly prior to powder coating them. What steps should we take to ensure that we are getting a quality finish that will meet the performance expectations?

A: As always, it is suggested that you start with the end performance expectations. Since your parts are used in the automotive and ACE industries, performance requirements will most likely include high corrosion resistance. To achieve this, the cleaning and pretreatment process plays a crucial role. First, you must review the types of machining lubrication used during the fabrication process and determine its ingredients. For example, is the lubrication an oil-based product or does it include other items such as surfactants, waxes, or other ingredients? Give this information to your pretreatment chemical supplier so they can determine the best chemistry for your cleaning stage(s). Also, depending on a few variables, they can determine whether the parts should be processed in a spray application or an immersion tank. Remember, if you do not remove the oils and other contaminants, they will be captured below the conversion coating and powder layers, leading to a premature failure. The next step will be to determine which type of conversion coating will meet the corrosion resistance requirements. Again, your chemical supplier can explore whether an iron phosphate, advanced pretreatment chemistry such as zirconium, or a zinc phosphate chemistry would be best suited for your product. To determine which scenario would work for either the cleaning or conversion coating, send some test parts to the chemical supplier’s lab so they can run trials. By changing the variables, you will be able to see which method and chemistries best meet your performance requirements.

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