Updated: October 18, 2024
Powder-coated metals could present a challenge when you need to bond two surfaces using adhesives. It's best to know exactly what you're dealing with before investing in a hot glue adhesive.
What is Powder Coating?
Some people think that powder coating is a type of painting technique. This isn't the case at all. Powder coating is essentially a thin layer of plastic powder that has been sprayed onto a surface and then cured under heat to form a protective skin. The most common types of plastic powders used are thermoplastic or thermoset polymers.
In particular, powder coating is often used on metal for a consistent color finish. The hard finish is more robust than paint, and it has many benefits including the ability to protect the metal from corrosion, scratches, or chipping. You may find powder coated metal on trailers, truck bodies, patio furniture, industrial equipment, and more.
Problems with Bonding Powder Coated Surfaces
You can bond powder coated surfaces both before and after the powder coating is applied, but the trick is ensuring you get a strong bond. While there are several glues for metal, not all of them can bond powder coated surfaces. Bonding powder coated metal is a lot more difficult than bonding a painted or raw metal surface, and an adhesive that works on raw metal may not work on powder coating.
Some adhesives use a type of solvent to etch into the powder coating, but some powder coatings are manufactured with a high resistance to solvents which stops the adhesive's etching mechanism from working. The adhesive you use needs to be compatible with the resistance of the powder coating.
Another potential issue when bonding powder coated materials comes from the additives in powder coatings. All powder coatings use additives in their formulations to improve durability, control gloss, or improve UV stability. Unfortunately, these additives can also affect the adhesive's effectiveness. A talc, wax, or slip agent additive, for example, can make it more difficult for an adhesive to bond to the surface. Polytetrafluoroethylene (PTFE) is another common additive that makes the powder coating hydrophobic and lowers the material’s surface energy. In general, lower surface energy materials are harder to bond.
The Best Glues for Powder Coated Metal
There are a lot of glues on the market, but you need the right one for bonding powder coated surfaces. Fortunately, we have experts in the adhesives industry that can help. Below are a few of our recommendations for the best adhesives for powder coated metals.
Infinity MMA 415HT - This high-temperature MMA can bond metal substrates both before and after the powder coating process. It requires little surface preparation and has a medium working time. It's high impact resistance, fatigue-resistance, and great strength make it ideal for harsh environments.
Infinity Bond MMA 420 powder coating adhesive - This two-part adhesive is designed with bonding difficult substrates, like gluing powder coated metal, in mind. It has a slow set speed with a work time of about 20 minutes, so it is great for larger applications or if you need time setting your substrates. The MMA is also weather-resistant and impact-resistant to meet the needs of applications in harsher environments. It comes in 50 ml or 450 ml cartridges.
3M DP460 - With its outstanding shear and peel adhesion, this 3M epoxy adhesive is great for high-performance, impact-resistant bonding applications in harsh environmental conditions. It has a 60-minute work life to give you plenty of time to adjust the substrates before curing occurs. It also meets safety standards related to ASTM test standards, toxic gases, flame retardance, and more.
3M DP8805NS - This high-performance, two-part 3M acrylic adhesive has excellent shear, peel, and impact performance. Because it has an exceptionally fast strength build rate and a work life of four to ten minutes, you need to work faster than you would with an epoxy. It also has the added benefit of being lower odor than most other acrylics. You can purchase this product in duo-pack cartridges as well as bulk containers.
Infinity Bond PUR MP75 - This product is a general purpose, polyurethane reactive, hot melt adhesive designed to bond to various substrates. A medium-fast-setting adhesive, it eliminates the need for pins and staples as well as reduces sanding and puttying after curing. The product also has a UV indicator to allows easier visibility under black lights.
For Pre-Powder Coating
Depending on your application, you may be looking for a sealant to be applied before the powder coating process. This sealant can create a protective layer to keep the powder coating from entering any gaps. It can also help you get a smooth and durable powder coated finish powder.
Unfortunately, many sealants are not compatible with the powder coating process. The temperature can get too hot for too long, plasticizer migration may occur, and discoloration of the powder coating finish is possible. But, recently a new product has come out that does not have these issues.
SikaSeal 330 high temp seam sealer is designed specifically to be applied before the powder coating process. Unlike some similar products on the market, it can withstand temperatures up to 446°F (230°C) and has no read through for a high-quality looking finish. It also is compatible with any color powder coating and maintains its flexibility after curing.
Make the Right Choice
Bonding powder coated metal can come with its challenges but not if you have the right product. If you need help determining what adhesive to use for your application, we want to help. Contact us today to speak with one of our adhesive experts. They can answer your questions as well as offer guidance on what products may work best for you.
