Powder coating is a popular method of applying a decorative and protective finish to metal surfaces. The powder coated surface creates a durable, uniform covering that resists corrosion and abrasion.
But what if you need to change the color after powder coating, or touch up flaws? Can you paint over an existing powder coated surface? The short answer is yes, you can paint over powder coating with proper preparation.
While challenging, it is possible to get paint to adhere to the ultra-smooth powder coated finish. This requires abrading the surface for the paint to grip, and using specialty primers and paints designed for metals.
Painting Over Powder Coated Metal
Powder coating, which involves applying colored polymer powder with an electrostatic charge, leaves an exceptionally smooth surface. This makes getting paint to stick to powder coating difficult compared to other materials. But with the right steps, a high-quality paint job can be achieved.
Key factors for success when painting over powder coat include:
- Properly preparing the surface through cleaning and abrasion
- Using etching or bonding primers designed for metal
- Choosing quality enamels, urethanes, or epoxies for topcoats
- Allowing proper cure times between coats
In following prep protocols, patience and attention to detail will produce a paint finish that adheres well and provides long-lasting protection and aesthetics.
Why Paint Over Powder Coat?
There are several reasons you may need or want to apply paint over an existing powder coated metal surface:
- Changing color – If you want to update the look or match other equipment, painting is necessary to alter powder coating color.
- Touching up flaws – Powder coating can occasionally result in flaws like bubbles or debris in the finish. Painting over flaws provides a uniform appearance.
- Covering damage – Repairing scratches, chips or damaged areas of powder coating requires spot painting for an intact looking finish.
- Improving adhesion – Some coatings or wraps don’t adhere well to slick powder coat, so painting first provides a grippable underlayer.
- Custom designs – Intricate multi-color graphics, fades, and other effects can be achieved by painting over powder coat primer.
Surface Prep for Painting Over Powder Coat
Preparing the surface is vital when painting over powder coated metal. The ultra-smooth finish must be roughened to allow the paint to adhere mechanically. This is achieved through cleaning and abrading the surface.
Cleaning
Thoroughly clean powder coated surfaces to remove any oils, dust, or debris before sanding or abrading. Grease removers, solvent cleaning, or scrubbing with an abrasive pad removes contaminants.
Abrasion
The key is to scuff up the surface to enable the paint to grip and bond. Methods for abrading powder coat include:
- Sanding – Lightly sanding with fine 400+ grit sandpaper roughs up powder coating enough for paint adhesion.
- Sandblasting – For a heavy powder coat layer, sandblasting provides deeper abrasion for paint bonding.
- Chemical etching – Etching primers contain acidic compounds that chemically roughen powder coatings.
- Mechanical abrasion – Abrasive pads, scuffing pads, or wire brushes mechanically rough the surface when rubbed over it.
Avoid completely removing the powder coat layer. The goal is to scuff the surface without penetrating the bare metal below.
Priming Paint Over Powder Coated Metal
After properly abrading, the next step is applying a primer designed for bonding to powder coated metal. Primers serve two important roles:
- Provides a profile for the paint to adhere to mechanically
- Forms a chemical bridge between the powder coat and paint
Using a dedicated metal or etching primer is necessary for paint to grip the surface. The specially formulated primers contain ingredients to etch and penetrate powder coatings.
Types of Primers
- Etching primers – Contain acid compounds like phosphoric or tannic acid to chemically bond with powder coat.
- Epoxy primers – Provide excellent adhesion and corrosion resistance on metal surfaces.
- Zinc chromate primers – Adhere well while adding sacrificial corrosion protection.
- Bonding primers – Designed to bite into slick surfaces like powder coating and form a mechanical grip.
- Self-etching primers – Combines etching acids and primer resins into one product.
Primer Tips
- Thin coats of primer work best to avoid obscuring the powder coated surface.
- Allow the recommended drying time before applying the topcoat. This could be 1-2 hours or longer.
- Priming immediately after scuffing helps the primer grip the roughened surface.
- Spot priming only where paint will be applied saves time when not changing the entire color.
Using the right primer is crucial for paint success over powder coating. An etching or metal bonding primer adheres to the slick surface and gives the new paint something to hold on to.
Topcoat Paint Options Over Powder Coat
The topcoat applied over your primer should be a high-quality coating designed for metal applications. Some topcoat paint options include:
Enamels
- Alkyd enamels – Offer good flow and leveling over primers and glossy, durable finishes.
- Urethane enamels – Dry to an extremely hard, chemical-resistant finish perfect for industrial use.
- Epoxy enamels – Applied as two components, epoxy enamels are incredibly tough and protective metal coatings.
Urethanes
- Polyurethane paints – Contain strong bonding urethane resins for outstanding adhesion and abrasion resistance.
- Moisture cured urethanes – Single component urethanes that cure when exposed to humidity in the air.
- 2 component urethanes – Require mixing a catalyst and resin for specialized applications like automotive quality finishes.
Epoxies
- Polyamidoamine epoxies – Tough, protective amine-cured epoxies that resist corrosion and chemicals.
- Polyamide epoxies – Durable epoxies with excellent adhesion directly applied or as primers under other coatings.
- Fusion bonded epoxies – Applied as powder coatings and oven cured to form thick, protective coatings.
Quality paints designed for metal provide maximum adhesion, durability, and performance over your powder-coated surface.
Application Process Tips
Following some best practices during application can help ensure painting over powder coating goes smoothly:
- If possible, paint in a controlled environment like a paint booth to avoid dust landing in the fresh paint film.
- Apply paint using consistent, overlapping strokes while avoiding runs or sags.
- Follow the coating manufacturer’s instructions for film thickness and recoat times.
- Allow the full curing period before putting the freshly painted surface into service.
Attention to application details makes it possible to achieve a flawless, consistent painted finish over existing powder coat.
Powder Coating Over Paint
Another option is to go the other way and apply a fresh powder coat over existing paint. This also requires careful surface preparation to ensure proper adhesion.
Key steps for powder coating over paint include:
Surface Prep
- Abrade painted surface with sandpaper or abrasive pad
- Clean thoroughly with a grease remover
- Apply conversion coating to chemically etch and bind surface
Powder Application
- Use thin coats to avoid obscuring detail
- Gel coat may improve adhesion over paint
- Cure according to powder coating guidelines
This provides a durable, uniform powder-coated finish over old painted metal surfaces.
Common Problems Painting Over Powder Coat
While certainly achievable, painting over powder coating does present some potential problems to be aware of:
- Poor adhesion – Inadequate abrasion and unsuitable primer can cause paint to peel or chip off powder coating.
- Cracking or wrinkling – Applying paint too thick over smooth powder coat can lead to cracking as it dries.
- Mesh pattern imprint – Using a nylon abrasion media can leave a visible criss-cross imprint in the paint film.
- Bubbling – Outgassing from powder coat layers during cure can cause bubbles in the new paint.
- Color matching – Batch variances make exactly matching the color underneath difficult.
These issues can generally be avoided with proper surface prep and testing application techniques.
Signs Paint isn’t Compatible With Powder Coat
Sometimes a coating just refuses to stick to the preceding finish. Signs your paint may not be compatible with the cured powder coat include:
- Peeling or flaking off in sheets rather than chipping
- Wrinkling or cracking immediately after application
- Fish-eyeing or crawling away from the surface
- Poor flow and leveling over the surface
Incompatible or unsuitable paints will exhibit these issues right away before fully curing. If this occurs, the powder coat must be completely removed before repainting the surface.
Media blasting provides the most consistent method of removing powder coating to a bare metal substrate. Once stripped, the metal can then be prepared normally and painted with the desired coating system.
Removing Powder Coating Before Painting
In some situations, it may be better to completely remove the existing powder coated finish before painting rather than coating over it.
Reasons to consider stripping powder coating first:
- Severe damage or flaws in the powder coat
- Questionable pre-treatment before original powder coat
- Need for a wider range of color and finish options
- Incompatibility issues with painting over powder coat
Methods to remove powder coating include:
- Blasting – Soda blasting or media blasting with glass beads, aluminum oxide, or garnet quickly strips powder coating.
- Grinding – Using an angle grinder with abrasive discs or wheels mechanically removes powder coat.
- Chemical stripping – Immerse in caustic chemical baths designed to dissolve and strip powder coating.
Once stripped to bare metal, the surface can be pre-treated and painted in any desired manner without potential adhesion or compatibility problems of coating over powder coat.
Key Takeaways for Painting Over Powder Coat
The smooth, durable finish powder coating provides can make painting over it challenging. With the right process and products, it is possible to change colors or touch up flaws in powder coated items:
- Proper cleaning and abrasion allow paints to mechanically adhere
- Specialty metal and etching primers bond to slick powder coat
- Enamels, urethanes and epoxies provide tough, attractive topcoats
- Careful surface preparation is key to achieve great results
- Stripping the powder coat first provides the most painting options
By understanding the unique requirements for application over cured powder coat, you can end up with a professional looking painted finish atop this popular metal finishing method.
