Tested! Will Painting Over Rust Stop It From Spreading?

So, I got these cute chairs for $10 each from my local ReUse Center:

Before chairs

Problem is, the bases are a little bit rusty. Not terribly, but it’s there wherever the paint was scratched:

Light rust on chairs

I’d love to just be able to paint them. But does paint stop rust?

Paint stops rust from forming on rust-free metal. On metal that already has rust, specialty rust-neutralizing primers can be used to stop rust from spreading further. Non-specialty paints can be used to stop rust as well, but may not last as long on rusty surfaces.

But what should you use for your project? Lets go over these options in a little more detail!

Note: This blog contains affiliate links. If you click and make a purchase, I may receive compensation (at no additional cost to you.)

Painting Rust-Free Metal

Rust is also known as “iron-oxide,” and requires three elements to form: iron, water, and oxygen. Paint prevents water and oxygen from reaching the iron, so as long as your paint job is in-tact, rust won’t form.

However, if your object is going to live outside, the paint job will likely break down eventually. And while theoretically, you’ll run outside and throw another coat of paint on, chances are you won’t do that fast enough.

And then rust will form, and suddenly you’ll have to do more work to maintain your project.

Because of this, I recommend different routes for indoor projects versus outdoor projects.

Rust-Free Indoor Projects

This is the easiest situation. Your project either doesn’t have any rust, or the rust is really light, and it’s unlikely to be exposed to tough conditions where rust would form. My chairs fall into this bracket.

In this situation, you still want to prime your project, but mostly to extend the life of the paint job, not because you’re really worried about a future rust situation.

I recommend covering with Rustoleum’s Clean Metal Primer before applying your paint. It’ll both prep your metal so that the paint adheres well, and help prevent rust from forming in the future.

You can put pretty much any paint you’d like on top of it, since the primer alone should do enough to prevent rust.

Note that this is an oil-based primer, so you’ll need mineral spirits for cleanup (or just wear gloves so it doesn’t get all over your fingers!)

And yes, you can still apply a water-based paint over an oil-based primer. I recommend waiting a few days, and then testing in an inconspicuous area first just to be sure, though.

Rust-Free Outdoor Projects

If your project is going to live outdoors, it’ll need a little more protection than indoor projects.

I’d actually start the same way as I would with an indoor project, using the Clean Metal Primer referenced above. But I’d also follow it up with paint that is specifically formulated to stop rust.

I usually go with Rustoleum’s Protective Enamel, just because it’s easy to find and it’s always worked well for me.

(This post isn’t sponsored by Rustoleum, promise. In fact, I talked to them at a booth once, and they literally scoffed at me. They were not interested in my little site. But the paint is still good.)

Painting Rusty Metal

For metal that has rusted significantly, paint alone is a temporary solution. While it will temporarily cover the rust, the paint will break down quickly and in the meantime, the rust will continue forming underneath the paint.

Instead, it’s best to treat rusted metal before painting. Luckily, this doesn’t have to be difficult.

There are primarily two products I use to treat heavily rusted surfaces: Rustoleum’s Rust Reformer, and Rusty Metal Primer.

Both products can be directly covered with paint, and both seal the rust and prevent it from spreading further. Both work best when any loose rust has been brushed off with a metal brush before application.

However, Rustoleum’s Rust Reformer is primarily meant for automotive use, and because of that, should only be applied to rusty surfaces. It does not act like a primer on clean metal.

This means if you have a project that’s rusty in some places, but still clean in others (like my chairs!) Rust Reformer would be a poor choice. It should only be applied directly to rust.

It’s a great choice when you’re painting something that’s completely covered in rust. Rust Reformer converts the rust to a paintable surface and prevents future rust from forming. It’s awesome at what it does, but it doesn’t work on rust-free metal.

The Rusty Metal Primer, however, can be directly applied to both rust and clean metal. It’s the way to go if you’ve got a project that’s pretty rusted, but clean in places as well. That way, you don’t have to switch between multiple products for the rust vs. rust free areas.

Regardless of which rust base coat you use, either product can be directly followed with paint.

An Example Case

Since my chairs weren’t significantly rusty, they were perfect for the Clean Metal Primer. Three months later, they’re still looking great!

Painted chair base

I did all three chairs in a single day, and I love how they turned out. I can’t get over how good they look, so even though it has nothing to do with rust, here’s a picture!

Finished previously rusty chair

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