Can You Paint Over Rust? (Explained!)

No one likes the look of rusted metal. So, can you paint over rust to cover it? 

You can paint over a rusted metal if the surface isn’t damaged. In this case, remove the loose rust by sanding, cleaning the surface, and apply paint. 

However, if the rust has eaten through the surface or created holes and dents in the frame, you shouldn’t paint over it because it won’t stop the rust from spreading. In this case, the best thing to do is to either fill the holes or replace the metal altogether.

Do You Need to Remove it?

Do You Need To Remove Rust Before Painting?

You must remove rust before painting. That’s because rust (or iron oxide) is a loose material. So, if you paint over it, the loose material will cause cracks and splits on the finish.

Also, since there’s rust on the surface, the paint won’t stick properly to the surface. Instead, the coating will stay over the rust material leading to poor adhesion between the coating and the metal.

The reddish-brown substance known as rust is made from the reaction of iron, oxygen, and moisture or water. When the surface is exposed to constant moisture and air (oxygen), a reddish-brown substance (rust) starts to form over it.

Rust is flaky and weak and can break down under minimal contact. So, when you apply paint over it, its flail structure won’t be able to support and carry the paint coating.

Instead, it will break into small pieces underneath the coating and cause cracks and splits on the finish. After a while, the entire paint coating will peel and fall off the surface. That’s why you should remove rust before applying paint. 

To remove the rust, scrape it off and sand down the surface with sandpaper. Afterward, you must wipe and clean the surface to get rid of the leftover. When the metal is smooth and rust-free, you can apply the paint. Optionally, you can also apply primer over the surface. 

Does Paint Stop Rust?

Painting can stop rust only if it hasn’t penetrated the metal frame yet. The paint will cover the surface and prevent it from growing. However, if it has penetrated the surface, painting won’t stop it. In this case, the damaged metal will continue to release rust and will cause the finish to blister and come off.

Rust is caused by two major factors; moisture (or water) and oxygen (or air). When a metal surface is exposed to these two factors, the iron compounds will react and form iron oxide (rust). However, if you apply moisture-resistant paints over it, it will shield the surface from air and moisture, preventing it from growing.

Since it protects metal from air and water, the rust will stop growing. So, painting stops it, but only if the rust has affected the surface of the metal and not the metal frame. 

If it has penetrated the metal frame, painting won’t stop it. That’s because it means the frame is weak and has holes. So even if you paint over it, the weak frame will still release rust and metal shavings underneath the finish, causing it to come off.

How To Paint Over Rust?

You need a few tools to make the process easier:

  • A scraper or trowel
  • Primer
  • Auto body filler
  • Sandpaper
  • Clean rags
  • Vinegar
  • Breathing protection
  • A pair of work gloves
  • Metal paint

1. Scrape Off The Rust

Remove The Rust

Remove as much rust as you can from the metal surface. To do this, use a flat metal object such as a putty knife or trowel. You don’t have to remove all the rust, just remove the loose particles. 

Important: Wear gloves and safety goggles while doing it.

2. Sand The Surface

Sand The Rusted Metal

Sanding helps to remove loose rust particles, so you can’t paint without sanding. If you do, there will still be loose rust on the surface, which can cause the finish to crack and peel off. So, sanding isn’t optional. 

Here’s what will happen to the paint coating if you don’t sand:

  • It won’t stick to the metal as it should.
  • It will be affected by stains and can eventually turn brown, especially if the finish is transparent.
  • The coating will take longer to dry.
  • It will blister and eventually fall off.

To sand it, use fine-grit sandpaper. Sandpaper can get dull fast while sanding it, so get as many sandpapers as possible. Instead of sandpaper, you can also use a power sander. 

3. Wipe and Clean The Metal

Wipe and Clean The Metal

Sanding produces a lot of dust, so you must wipe and clean the surface with vinegar. Vinegar is a mild acid that will dissolve and remove filth and reddish tints from the metal surface.

Baking soda and rubbing alcohol also work in case you don’t have vinegar. If you don’t clean the surface, the finish will appear reddish or brown due to the effects of rust. 

To clean the metal, damp a rag with vinegar and use the dampened rag to clean it. You can also pour vinegar directly to it and use a rag to wipe the surface. 

4. Fill Holes In The Metal (Optional)

Fill Holes In The Metal

If the metal surface has holes or imperfections, fill them with auto-body filler. The auto body filler is a paste-like product that helps to cover and seal holes in metal surfaces.

If you don’t cover or fix them, the paint will be sucked into the frame and won’t appear smooth.

5. Apply Primer

Apply A Coat Of Primer Paint Over The Metal

Apply 1-2 coats of metal primer using a brush.

6. Apply The Paint

Apply The Paint

Once the final coating of primer dries, apply metal paint over the surface. The metal paint is designed with additives that will prevent rust from growing again. To apply it, use a brush or sprayer and apply 2 coats. Optionally, you can seal the finish with a waterproof sealant.

FAQ’s

Is There A Paint That Removes Rust?

Technically, no paint will remove rust because it will develop as long as the surface is exposed to moisture and air. However, some types prevent it from growing and spreading.

These paints are formulated to be thick, moisture-resistant, and heat-resistant. They prevent moisture from affecting the metal surface, so rust won’t be able to grow or spread. Rust-oleum is a great choice. 

Can Rust Bleed-Through Paint?

You must scrape the rust to prevent it from bleeding through the finish. You also must clean the surface with vinegar, and apply 1-2 coats of stain-blocking primer. 

Final Words

You can paint over rusted metal as long as the surface isn’t damaged or has holes. All you have to do is to remove the rust, clean the metal surface, apply a coat of primer, and then paint it. 

However, if the surface is damaged, you must fill the holes, try to find the cause of the rust and fix it, apply a primer, and then pain it. Never paint directly over rust as the paint won’t stick and will peel off. 

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