Here Are the Top 3 Methods of Powder Coat Removal Including the One the Pros Usually Choose
Powder coating is one of the fastest growing technologies in highly industrialized countries. It uses an advanced electrostatic method to charge each particle that forces it to adhere to an electrically grounded surface. This effectively melts the powder, so it fuses into the surface being coated. Once applied, the powder is permanently adhered to the item.
A good powder coat is very long-lasting and durable, providing extremely high protection to the underlying surface at a very attractive price. It’s used both industrially and by consumers, but for a coating to be successful the surface must be properly prepared.
There are times a powder coat removal is necessary, including
- Updating the coating or refinishing it.
- Changing the color.
- Failure of the coating.
- Cleaning the racks and hangers after coating an item.
Fortunately, powder coat removal is possible in most cases. There are a few methods for doing this, but the most popular are chemical strippers, thermal baking and abrasive blasting, also known as sandblasting. Each may be appropriate for some projects and not for others. Here are all three, along with their advantages and disadvantages and where they are most useful. They’re presented in ascending order of popularity, with the last being the most used by professionals.
3. Chemical Stripping
There are two basic methods of chemical stripping: hot and cold. Hot stripping uses a bath of warm solvent, around 80°, that quickly softens and dissolves the powder particles. The coating either falls off or is washed off in a secondary rinse or bath. Cold chemical stripping uses either a bath or application by brush, and often takes longer than hot stripping. If a part is delicate, you may have no choice but to use a chemical stripper, but make sure you understand the disadvantages.
Chemical powder coat removal is usually relatively fast and leaves a uniform surface. However, the disadvantages lead most commercial and industrial users to choose other methods. The downsides include
- The substrate isn’t etched, leaving no surface profile for new coating adhesion.
- It’s dangerous – the chemicals are noxious, smell terrible and can burn your skin on contact.
- Cold weather can stop the process.
- It can be expensive.
- The environmental issues and costs can outweigh the benefits.
2. Extreme Heat
By using ovens that warm up to between 300-650° (depending on the method), the powder coat and resin are broken down, leaving a non-adhering ash residue that can be washed or sandblasted off. Fluidised bed stripping uses a liquid medium or sand to transfer the heat, which also removes the residue. The bake-off method uses an oven to heat up the item, leaving ash you’ll have to wash or blast off. The extreme heat burn-off method uses temperatures up to 650° to ignite the coating, removing it very quickly.
Thermal stripping can be the fastest method, but it does require equipment to create the high heat. The item also needs to be able to withstand the temperatures, but the main disadvantage to this method is that, like chemical stripping, the substrate is left without a good surface for coating.
1. Abrasive Blasting
Also called sandblasting, abrasive blasting powder coating uses a grit such as garnet, plastic or crushed glass to strip the powder off the substrate. This is the most popular method of powder coat removal, for a variety of reasons, including
- The right grit will leave a perfect surface for new coat application.
- It’s usually the least expensive method.
- Since the other methods may also need sandblasting for surface prep or residue removal, the whole process is streamlined.
Of these reasons, the surface preparation may be the most important. Without prep, the new coating won’t be effective at protecting the substrate and often won’t adhere properly. Most professionals choose abrasive blasting for powder coat removal. However, in specialised circumstances (such as a delicate item), you may be forced to choose one of the other methods.