Metal can be a pain to paint because it doesn’t have the same surface qualities as wood. It’s common for people to get frustrated with painting metal because of how difficult it can be. But painting metal doesn’t have to be so hard! This guide will answer the most common questions about primers for metal and how you should prepare your surfaces before you start painting.
TOOLS & MATERIALS
These are recommendations! With these items, you can achieve results much faster and save your lungs and health!
- Stiff-bristled wire brush
- Sanding block
- Drop cloth
- Cotton cloths
- Spray primer
- Spray paint
- Safety glasses
- Dust mask
- Clear spray lacquer
Step-by-step guide on how to prepare the metal surface for painting
1. Cleaning metal before painting
To prepare new metal surfaces for painting, clean them with mineral spirits to remove grease and apply a rust-inhibitive primer. Remove dust from painted surfaces using a clean, dry cloth, de-gloss the surface with light sanding, and then wipe with mineral spirits to ensure good adhesion. Wash the surfaces with a mild detergent solution and allow them to dry.
New metal surfaces such as steel and aluminum should be degreased with a solvent (such as lacquer thinner) or TSP (Trisodium Phosphate) before priming unless you’re using an etch primer designed for raw steel that has not been previously painted.
2. Remove loose and peeling paint
You can remove old paint by hand wire brushing, sanding, or scraping if it is in poor shape. Because these methods are time-consuming and rarely provide the expected results, many professionals utilize power tool cleaning, which may help remove paint rapidly.
However, power tools have one disadvantage: they can polish metal surfaces and remove the texture, causing a smooth appearance.
If removing paint from metal surfaces is a concern, ask if a power tool can be used to minimize damage or whether another method will suffice.
3. Remove rust
When metal is being prepared for paint, it’s critical to check for rust so that the paint will adhere properly to the surface. To return slightly rusted metal surfaces to their original condition, use a brush to remove loose rust, sand the area, and apply a high-quality rust-inhibitive primer (e.g., Rust-Oleum Rust Reformer).
Wash, rinse, and dry the surface. To ensure a clean work environment, remove all rust with a wire brush or emery cloth before priming. Make sure to follow the manufacturer’s specifications for cleaning metal surfaces before painting. Sand off any loose paint from the primer coat that may be adhered to the steel surface.
If the metal surface has deep rust, you may consider using a commercial acid treatment to remove it before applying primer and topcoat finishes. Strip old paint off wood siding with an electric heat gun or propane torch (be careful not to burn surrounding structures). Allow steel areas that are inadequately protected from rain to dry for several days before priming.
4. Repair small holes and dents
Remove any loose paint or debris from the area, sand it until you reach bare metal, and clean it with a degreaser and mineral spirits. Inject an appropriate epoxy-based composite into small holes and dents.
Apply epoxy filler to the perimeter of larger holes, cut a piece of fiberglass mesh approximately one inch greater than the area, and press it into the epoxy. Apply resin over the mesh with a brush to repair minor holes or dents in metal surfaces.
5. Apply the Primer Coat
Priming is an important stage in preparing metal for paint, particularly if the area is exposed to water. When selecting the appropriate primer, consider the type of metal to be coated and desired appearance, performance criteria, and environmental conditions.
In the first place, water-based (latex) primers should not be used on metal surfaces because moisture might seep through and cause paint to fail within weeks or months. Rust converters and galvanized metal primers are two types of metal primers that experts recommend.
A rust converter helps keep rust from recurring and makes a rusted surface easier to paint. At the same time, a galvanized primer is appropriate for metals (such as aluminum) that prevent paint from sticking. You can also buy iron oxide and zinc chromate primers for use on most metal surfaces, including iron and steel inside and outside.
You can also purchase epoxy primers that are more expensive than other primer types that provide excellent adhesion to metal surfaces. Additionally, applying the right amount of paint (thinner coats will peel); if you let too much time elapse between coats, the previous layer may not properly bond with the next coat.
Is primer necessary for painting metal?
Primer is necessary for painting metal. It’s a coating that prepares the surface and creates a more uniform finish with the paint.
Where should I prime on my project?
You can prime your entire piece if you’d like, but it’s recommended to do at least one coat of primer on any bare metals as well as any rusty areas or surfaces where rust restoration treatment has been applied.
What kind of primer should I use?
A water-based latex primer will work best for most projects without taking too long to dry. VOC-free (Volatile organic compound) formulations are also available, making them excellent options for indoor projects or homes with pets! If you need something more substantial, consider using an alkyd enamel primer for increased adhesion and durability.
When should I prime my metal surfaces?
You can apply your primer when the surface is clean and dry, typically after it’s been degreased with a chemical cleaner or solvent such as acetone.
What kind of paint should I use?
There are lots of different kinds of paints that can be used to finish metal! Here’s a list:
- Acrylic-based paints (great for indoor projects)
- Oil-based enamel (ideal for high heat situations like engines, the outdoors, or even BBQ grills!)
Specialty products such as:
- powder coating
- automotive finishes,
- and industrial coatings.
More info in my article Primer Guide: The Best Primers for Metal Surfaces.
What kind of topcoat do I need on my finished piece?
A quality clear protective lacquer is recommended so you can protect your painted surface from scratches, dirt accumulation, or UV exposure.
Do I have any other options if I don’t want to use an oil-based primer?
You could try using epoxy instead, which will dry faster and stick better. It’s an excellent option for metal surfaces that will be exposed to constant or high heat situations because epoxy is known for its durability!
What should I do if my primer doesn’t seem like it’s sticking?
If your primed surface has been allowed to dry completely, but you’re still having difficulties with paint adhesion, try sanding lightly all over the primed area before applying another coat of primer. Sometimes this can help roughen up the surface, so paint sticks more easily. You could also consider using an undercoating spray which acts as a bonding agent between coats of paint, allowing them to bond together without peeling or chipping off later on.
What about painting bare steel?
This type of project would only require you to use an oil-based primer or even straight-up spray paint without any undercoating.
What about rust? Should I prime over it before painting my metal surface?
If you’re working on a project where the bare metal has already begun eroding, flaking off in pieces, or re-appearing after being painted previously, then yes – consider priming your entire piece! You can also apply extra coats of both oil and latex-based paints if it’s still not sticking well enough for your liking, but be sure that there aren’t too many crevices that might trap moisture against the rusted area later down the road. If only certain parts show signs of corrosion, focus on those specific areas and avoid the rest!
What should I do if I’m looking to refinish an old piece of metal furniture?
You’ll want to sand off any loose paint and rust before applying a primer. If you’re having trouble getting into small crevices, then try using steel wool, but be sure that it’s extra fine so as not to damage your surface further. For large areas, use an orbital sander or some protective eyewear and manually sand by hand for best results.
Does metallic paint need a primer?
You might be able to skip using a primer on bare metal surfaces because they’re often made of very tough metals which won’t require much protection.
How many coats of primer on metal?
Primer for metal should be applied in two light coats. Allow each coat to dry before applying the next one.
How to prep bare metal for primer
- Mask off any areas you don’t want to be affected by the primer and sand the surface with fine sandpaper or steel wool.
- Fill in any holes or cracks in the metal with a suitable metal filler. Allow the filler to dry before sanding it smooth.
- Apply a coat of primer to even out any irregularities in the surface and allow it to dry. Apply another coat for better coverage and allow it to dry.
How to remove primer from metal
Remove the paint by scraping it off with a putty knife. The primer may start to separate from the metal, so gently pry it away. Scrape off any residue that is left, then wash the metal with soap and water.
How to remove oil-based primer from metal
Oil-based primer is more complicated to remove than latex; there are no effective solvents for the job. The best way to remove it from metal is by sanding or scraping until all of the paint has been removed.
Wipe off any residue with a cloth dampened in mineral spirits and let it dry completely before applying more primer coats over the top.
These are the steps to prepare metal surfaces for paint or primer coats before painting them with your desired color scheme. This guide has answered common questions about metal surface preparation and its various uses in applying different types of paints, stains, and finishes. If you have any other concerns regarding preparing metals for paint application, feel free to ask them!