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The Importance of Sandblasting Before Powder Coating

Sandblasting is one of the most important steps you can take when powder coating metal parts. It’s an essential part of cleaning metal before powder coating, ensuring the powder coat lasts a long time and isn’t harmed by contaminants on the metal surface. Sandblasting comes with many benefits, and using it properly can greatly improve the quality of your powder coating and the protection of your metal parts.

Find out more about sandblasting and how it can help prepare a metal surface prior to powder coating. Additionally, you may want to be aware of the required steps for powder coating preparation, which we will explain below.

What Is Sandblasting?

Sandblasting is a kind of metal preparation process designed to etch or clean a surface. Many people use it to clean off metal surfaces before they powder coat them. When someone sandblasts a metal, they’ll use a pressurized gun to propel extremely fine materials at incredibly high speeds toward a surface. 

While sandblasting gets its name from the type of material it propelled when the technology was first developed, it doesn’t always use sand. Other very fine bits of materials are also used and are more common, such as powdered abrasives, copper slag, coal slag, silica sand, walnut shells and steel grits. 

To properly sandblast a metal surface, a user will load the pressurized sandblasting gun with these fine blasting materials. This gun will generate high-powered pressure to propel the materials forward. Since the sandblasting gun makes the materials fly forward quickly and at high pressure, the sandblasting technique effectively removes any contaminants or dirt on metal surfaces.

Do You Have to Sandblast Before Powder Coating?

Sandblasting before powder coating is a necessary step to take. If you’re wondering if the metal has to be bare to powder coat it, the answer is yes. Sandblasting is the best method to clear it. 

Proper powder coating preparation requires metal surfaces to be entirely clear of any finish or dirt that could cause the powder coating to not adhere to the surface. Besides removing contaminants, it’s essential to eliminate the old coat of paint or powder. Stripping the prior coat paves the way for you to apply a newer powder coating layer evenly across the surface. Sandblasting the prior coat also ensures your new coat effectively sticks to the metal surface.

Additionally, when you don’t take the time to clean a metal surface with sandblasting, it’s much more likely that your powder coat will suffer from peeling, bubbling and cracking from poor adhesion. Not using sandblasting can also result in the powder coating having a reduced life span. If you want your powder coating to last a long time and provide a smooth outer surface, you should use sandblasting.

Benefits of Sandblasting Prior to Powder Coating

There are several advantages to sandblasting your metal parts before powder coating, making it an essential step for anyone who wants to properly prepare their metal components. These benefits range from providing faster cleaning and removing tough contaminants to giving powder coating a longer life span and causing the metal surface to be more friendly to bonding. With all the ways sandblasting can improve the powder coating process, savvy businesses know to use it to assist with metal cleaning. 

Below is some more information on the primary benefits of using sandblasting prior to powder coating:

  • Fast cleaning: A major benefit of sandblasting metal parts is the ability to quickly clean surfaces before powder coating. Since you’re shooting tiny particles at high speeds onto the metal surface, you can quickly clear off contaminants. Compared to manually scrubbing or sanding these contaminants off, it’s a much more time-effective process.
  • Effective removal of tough contaminants: One of the most obvious benefits of sandblasting is how it effectively removes even the toughest contaminants from a metal surface. Besides eliminating dirt and dust, it can also effectively remove tougher materials like rust and paint. Sandblasting ensures you get all these contaminants off your metal surface, helping it be as clean as possible before powder coating.
  • Greater bonding on the metal surface: It’s also important to sandblast metal parts because the process leaves minuscule scratches on the surface. These tiny scratches make it easier for powder coats to bond with and sink into the surface. With an easier bonding process, your powder coating will look much more even and uniform on the metal’s surface. Additionally, you’ll see greater powder coating adhesion over a longer period.
  • More effective for angles and curves: Some entirely flat materials can be manually sanded before powder coating instead of being sandblasted. However, most metal parts will have curves and angles, which are very difficult to sand evenly by hand. Sandblasting makes it much easier for people to smooth out the surface of a metal part and remove contaminants from hard to reach areas. This more efficient method saves you time and produces smoother coats.
  • Longer life span for powder coating: Sandblasting is also critical as it helps improve the powder coating’s life span. Since sandblasting removes contaminants that could cause peeling, bubbling and cracking, you can safely apply the powder coat to the surface. As a result, your powder coat will stick to your metal part for a longer time, reducing the frequency of needing replacement coats.
  • Exceptional reusability: Since sandblasting doesn’t do any structural damage to a metal part, you can reuse it as much as you like. Every time your metal part needs a fresh powder coating, you can use sandblasting to remove the old coat and any contaminants that might be on the surface. When you can sandblast your metal surfaces any time you want, you can better protect them over the long term, making sandblasting technology and services a worthwhile investment.

Best Blasting Media for Powder Coating

Before powder coating, you’ll need to use blasting media in the sandblasting gun to remove any contaminants. When you search for blasting media, you’ll have multiple options to select from, so it’s important to choose the right one. Coal slag is a popular option, as it’s cost-effective, lasts for a while and leaves a good profile. It also strips rust and paints quickly.

Another good blasting media is aluminum oxide. While it’s more expensive than coal slag, it’s even more effective at removing paint and rust. Aluminum oxide is also an extremely aggressive media, allowing it to remove prior powder coats fast. It tends to leave a great profile on iron and steel, and it doesn’t produce as much dust as coal slag, leading to faster clean up. You’ll likely want to steer clear of this blasting media on softer metals, as it can leave too much of a profile.

While you might think sand is appropriate as a blasting media, it’s usually not a good choice. Even though sand is the cheapest option available, it produces a great deal of dust, which can make it hard for you to see while sandblasting and could contaminate the metal parts. Additionally, the silica dust produced by sand can lead to severe lung damage, and the only safe way to use it is to wear a supplied-air breathing system. 

CAN YOU POWDER COAT OVER RUST?

It’s not recommended to powder coat over rust. Like other contaminants, rust can affect the powder coat’s quality after application. When you place powder coating over a rusty surface, the rust can cause outgassing, bubbles and various imperfections in the powder coating, resulting in a poor finish. You also shouldn’t powder coat over rust because rust will continue to spread and start flaking off. When the rust flakes off, your powder coat will come off with it. 

Luckily, sandblasting can handle rust, even the tougher variety. By using sandblasting to clear all the rust off the metal parts, you can prevent the negative effects of leaving it there. Sandblasting your rusty metal components will save you a significant amount of time and money in the long run, as you won’t get bogged down continuously adding powder coating to areas that rust has damaged or caused to flake.

How to Prep Metal for Powder Coating

Metal prep for powder coating is a crucial step to take. Powder coating preparation involves a multi-step process to ensure the metal part is ready for a professional to sandblast and powder coat it. Since cleaning metal before powder coating is crucial to getting the most out of the process, you should know how to prep for powder coating. Additionally, you’ll want to know the best practices for safety and proper sandblasting during metal prep.

Review some of the primary steps for the powder coating process below:

  • Gather supplies: Before you begin prepping the metal, you should gather your supplies. To complete the prep work, you’ll need high-temperature tape, vinyl gloves, a clean rag, degreaser and a screwdriver or wrench.
  • Remove parts: With your screwdriver or wrench, remove the metal part’s bolts and nuts. You’ll want to remove these elements due to the need for bare metal during the sandblasting stage.
  • Wipe bare metal with a clean rag: Once your metal is bare and you’ve removed all the bolts and nuts, you’ll need to wipe the part with a clean rag. To get rid of any oil or grease on the metal surface, you should use your degreaser. After completing this stage, wear vinyl gloves whenever you’re handling the metal part to avoid contaminating the surface with your oily fingerprints.
  • Identify areas you don’t want to powder coat: After you’ve wiped down the metal part, move on to identifying areas you don’t want to powder coat. With these spots identified, utilize high-temperature tape to protect them from the sandblasting process and powder coating. If your metal part has any holes exposed designed to hold bolts or screws, fill them with a high-temperature plug.
  • Suspend metal part in the air: While still wearing your gloves, find a way to suspend your metal part in the air. When you hang the metal part in the air, you’ll expose all of it for sandblasting and powder coating. Many people choose to hang the metal with a chain.
  • Put on safety glasses and a respirator: With the metal part hanging in the air, you should prepare yourself to use the sandblaster. Since the sandblaster will shoot out many tiny particles at high speeds, wearing a respirator and safety glasses is a must. Before you begin handling the sandblaster, ensure you’re properly wearing your safety gear.
  • Prepare and use sandblaster: Once you’re wearing the relevant safety gear, attach your sandblaster to the air compressor, with the sandblaster filled with your chosen blasting media. Begin spraying the metal part with the sandblaster, ensuring you do so evenly and carefully to blast every section of the metal part.
  • Clean area: After using your sandblaster, don’t immediately move on to powder coating. Instead, sweep the floor to remove any debris or dust in the area. If contaminants are left on the floor, they could end up sticking to your powder coating during its application. By sweeping, you increase the chance that your powder coating lasts a long time and doesn’t crack or peel prematurely.
  • Disconnect sandblaster and prepare powder coating: With the area swept clean, disconnect your sandblaster from the air compressor. After removal, you can connect the corona gun to the air compressor. You’ll use this gun to apply the powder coat to the surface. Ensure you’re still wearing your safety gear as you fill the corona gun with your powder coating.
  • Spray the item with powder coating: Once the gun is filled with powder coating, begin spraying the metal item with it. You should spray the powder coating much like you’re using a can of spray paint, doing so in even and short strokes. As you spray, check to see if you’ve applied it evenly and that you’ve covered every angle and surface. If you want to apply a second coat, you can do so after you’ve evenly applied the first coat.
  • Cure metal Item: After powder coating the item, you’ll want to cure it. To do so, preheat the oven to 400 degrees Fahrenheit. Once the oven reaches this temperature, place the metal part in it for 10 to 25 minutes, letting it cure. When the curing is complete, wait for the metal part to cool down before taking it out of the oven.

Contact APX York Sheet Metal for Powder Coating Services

With all the steps and equipment needed to sandblast and powder coat a piece of metal, you may want to turn to a professional. At APX York Sheet Metal, our team of powder coating experts is ready to help. Our ability to handle jobs of various sizes, fast turnaround time and exceptional customer service make us the go-to option for our clients. We can powder coat several metal parts, such as front panels, metal brackets and sheet metal boxes.

View our powder coating services to see what we can do for you. If you have any questions, please contact us or request a quote

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