Painting rusted metal can seem like a daunting task, but with the right preparation and materials it can be made to look as good as new. Proper preparation is key when painting rusted metal to ensure the paint adheres and lasts. This guide will walk you through all the steps needed to get rusted metal ready for a fresh coat of paint.
Clean and Remove Loose Rust
The first step when prepping rusted metal for paint is to clean the surface thoroughly and remove any loose rust or flaking paint. Here are the best ways to clean and remove loose rust from metal:
- Use a wire brush: A stiff wire brush is highly effective for scrubbing off loose rust and flecks of paint. Scrub the brush over the surface in different directions to get into crevices. This works well for lightly rusted items.
- Try sandpaper: For small rust spots, use coarse grit sandpaper to sand away rust down to bare metal. Start with 60-80 grit paper and work up to 120-150 grit to smooth the surface.
- Use a grinder: For heavily rusted metal, an angle grinder with a wire cup brush attachment can remove rust quickly. Wear eye protection and work the grinder carefully over the surface to avoid damaging good metal.
- Soak in vinegar: Soaking rusted items in undiluted white vinegar for a few hours helps loosen rust and corrosion. Then scrub with a wire brush.
Thoroughly clean the metal once you’ve removed all loose rust. Wipe down with mineral spirits, denatured alcohol or other degreaser. Rinse with water and let dry completely. This prevents any oily residue from interfering with paint adhesion.
Sand Away Excess Rust
After getting rid of all loose rust, you’ll need to sand down any remaining rust spots to get to bare metal. Here are some tips:
- Start with coarse 60-80 grit sandpaper to remove bulk rust. Don’t worry about scratch marks at this point.
- Always sand in the same direction of the metal grain to avoid deep scratches.
- Use finer 120-150 grit paper to smooth everything out once the main rust is removed.
- Hand sanding works well for irregular shapes. Use a random orbital sander for large flat areas.
- Sand until you reveal shiny silver metal beneath indicating all rust is gone.
- Clean the surface again after sanding to remove rust particles. Let dry fully before painting.
Be sure to sand away rust from edges and crevices. Remaining rust under the paint will eventually bubble and flake the finish.
Apply Rust Converter (Optional)
For heavily rusted metal, applying a rust converter after sanding can help neutralize any remaining rust and improve paint adhesion. Rust converters contain tannic acid which reacts with rust and chemically converts it into an inert protective coating.
Here are some tips for using rust converter:
- Shake or stir converter well before applying. Use a chemical resistant brush or spray.
- Apply a thin, even coat over entire sanded surface according to manufacturer directions.
- Let it dry 24 hours. Rusted areas will turn black as the acid neutralizes the rust.
- Apply a second coat if needed for thick rust. Avoid any puddles or drips which can interfere with paint bonding.
Rust converter provides added protection if you are concerned about sanding away all rust or need to preserve delicate surfaces. Allow to fully cure before applying primer and paint.
Wipe with Tack Cloth
After all sanding, make sure to wipe down the metal with a tack cloth. This picks up any remaining dust or particles from sanding that could affect paint finish.
Lightly rub the tack cloth over the entire surface. Don’t apply pressure or you may snag the weave on rough edges. Change to a clean section of cloth frequently so you don’t redistribute particles.
Tack cloths are essential when painting metal to get a blemish-free professional looking finish. Never skip this step.
Apply Primer
Now you’re finally ready for paint! But first it’s crucial to apply primer designed for metal. Primer serves an important role:
- Creates a surface for paint to adhere to
- Seals and protects the metal from moisture
- Hides imperfections for a smoother finish
- Prevents rust from recurring through the paint
Use a quality metal primer like Rust-Oleum rusty metal primer or Krylon rust protector. Apply two thin coats allowing proper drying time between coats.
Follow all label directions for best results. Primer provides the foundation for your paint to last without flaking or peeling.
Topcoat with Paint
Once primer is fully cured, finish up by applying your topcoat paint. This could be a basic enamel spray paint or higher end automotive paint if you want a showroom quality finish.
Here are some topcoat painting tips for painted metal:
- Lightly sand primer with fine 220 grit sandpaper to help paint adhere.
- Use smooth spraying motions from about 8 inches away. Several thin coats are better than thick coats.
- Allow proper drying time between coats as recommended by manufacturer, usually 1-2 hours.
- Consider adding a clear coat for extra gloss and protection. This also allows you to buff out imperfections.
- Don’t handle or use the painted item for several days to allow paint to fully cure.
Properly prepping your rusted metal before painting is the most important step for success. But applying primer and paint correctly also ensures your fresh paint job will last without peeling or chipping. With some time and care you can make rusted metal look brand new!
How to Paint Rusted Metal FAQ
Painting over rusted metal to give it a new lease on life is very rewarding, but it can also seem intimidating for a first-timer. Here are answers to some frequently asked questions about painting rusted metal to ensure success.
Should I use etching primer on rusted metal?
Etching primers contain phosphoric acid that etches into rust and metal to create a better gripping surface for paint. This isn’t necessary if you thoroughly remove rust and sand the metal. Regular metal primer applied correctly is usually sufficient.
How do I stop rust from coming back under the new paint?
Thorough prep is key – remove all loose rust, sand to bare metal, and apply a primer made to prevent recurrent rust. If heavily rusted, using a rust converter before priming adds extra protection. Proper prep prevents rust from resurfacing.
What kind of paint adheres best to rusted metal?
For maximum adhesion, use a high-quality enamel spray paint formulated for metals, such as Rust-Oleum. The oil-based formula penetrates and seals rusty surfaces well. Latex and acrylic paints don’t bond as strongly to metal.
Can I just spray paint over rust without sanding?
Spray paint may seem to adhere at first, but skip proper sanding and priming at your peril. The paint will soon bubble, crack, and peel as unremoved rust continues corroding from underneath. Proper surface prep is mandatory.
How long does painted rusted metal take to cure?
Most spray paints fully cure in 24-48 hours. But it’s best to allow painted metal to cure undisturbed for 5-7 days before handling to prevent damaging the fresh paint. Cure times vary based on temperature and humidity. Read product labels for recommendations.
What kind of primer should I use on rusty metal?
For best results, use a primer specifically made for metals, such as Rust-Oleum Rusty Metal Primer. Make sure the label indicates it can be used to prime and paint over rust. The formula will contain anticorrosive properties to prevent recurrent rust.
Painting rusted metal takes work, but the results are worth it. With proper preparation and finishing, that old rust bucket can be ready for display in no time.
Conclusion
Painting over rusted metal can seem like a difficult job for an amateur DIY-er. However, armed with the right techniques and materials, even heavily corroded metal can be restored.
The key is proper preparation by thoroughly removing loose paint and rust down to bare metal before applying specialized primer and paint. Rust converter adds extra protection on badly rusted items. With patience and the right painting products, that old rusty chair or tool can look factory-fresh once again.
Painting metal that is already rusted requires more care to ensure the paint properly adheres and lasts without rust resurfacing. But with diligent surface prep and step-by-step application of primer and paint, you can successfully renew items damaged by rust to use and enjoy for years to come. With a little time and effort, you can make rusted metal look brand new again.