Does Painting Over Rust Stop it from Spreading?

Painting over rust

Are you having some rust troubles? If you’ve noticed every metal item you own has begun to rust, then it’s time to figure out what you can do to stop that rust in its tracks. 

Painting over rust can stop it from spreading. However, when painting over rust, make sure you adequately prepare the surface and use the right type of paint. 

In this article, I’ll share with you some tips and tricks for painting over rust. Painting over rust isn’t complicated, but it’s important to understand several principles to ensure the rust doesn’t return. 

Let’s jump in! 

Can Paint Stop Rust? 

Yes, paint can stop rust. Cars, knives, beams, and many tools are all coated with paint to inhibit rust. However, painting over rust is a different story and requires a little more thought. 

Before we understand how to paint over rust, we need to answer two questions:

  1. How does paint stop rust? 
  2. Rust neutralizer vs. rust coating

Let’s go over these two concepts in more depth. 

How Does Paint Stop Rust from Developing

Rust is also known as iron oxide. Rust develops when oxygen contacts iron in the presence of water. Water speeds up the conduction of the reaction, and salty water will speed up the rusting process even more. 

Iron. Oxygen. Water. Three pretty common things in the world. Unless you’re going for the old antique vibe, you probably don’t want to have red flaking rust all over your property. 

So, how can paint stop rust from developing? Paint is the shield between the iron in the metal and the oxygen and moisture in the environment. 

By coating your metal with paint, you’ll prevent moisture and oxygen from reacting with the iron. And, as a result, you prevent rust. 

However, what happens when the rust has already started? Can paint help you then? Below, we’ll go over this in more detail.

Rust Neutralizer vs. Rust Coating 

If you’re looking for paint to stop rust, there are two main options – cleaning and repainting the surface or using a rust neutralizer. 

We will go over the specific brands and types of rust paint and neutralizer in the next section. For now, here are a few things to know about each. . . 

First, rust preventing paint. This type of paint requires most of the rust to be removed before painting. Rust paint will be a better option for those projects that require a specific color – like a door or a metal chair.

Second, rust neutralizing paint. This type of paint is applied directly to the rust. There are many types of rust neutralizers. In general, rust neutralizers react with the rust to create a stable coating over the metal. Rust neutralizing coatings are best applied to projects where color isn’t a big deal, like the underside of a car. However, many times you can paint over the rust neutralizer (also known as a rust converter).

In the next section, we’ll go over some of the best rust-stopping paint. Then, we will discuss the best way to apply the paint to prevent rust. 

3 Types of Paint to Stop Rust 

Now, let’s explore several good paints for rust treatment. We will include both regular paint and rust neutralizers in this section. Many paints will work to prevent rust. This list is not exhaustive; however, it should point you in the right direction. 

Paint to prevent and treat rust:

  • Rustoleum – Rustoleum is a common paint used to paint metal. It can be painted with a brush or sprayed from a can. Rustoleum makes many types of rust-treating paints. They even have their own version of a rust converter. Rustoleum will hold up fairly well when applied to outdoor projects as long as you follow the instructions and apply the paint in the right environment. 
  • POR 15  – POR 15. The “POR” stands for paint over rust.  POR 15 is a rust converter. It is a professional-grade rust treatment that is built for heavy-duty tasks. One thing: POR 15 will need a protective coating if exposed to sunlight. Also, if you want to paint over POR 15, you’ll likely need to apply a primer.  
  • Corroseal – Corroseal is similar to POR 15 in that it converts the rust to a stable material. When using Corroseal, you don’t need to grind the rust completely from the metal. One advantage of Corroseal is that it will create a primer during the rust conversion process – this allows you to apply a nice colored paint later. Also, Corroseal is not reported to be as sensitive to sunlight. 

There are many more products for treating rust than listed here; however, this list will get you started in the right direction. 

In the next section, I’ll explain how to paint over rust. 

How to Paint Over Rust 

Now let’s go over some practical tips for painting over rust. This isn’t difficult; however, if you’re lazy with the process, you won’t fix the rust. 

We will go over two types of paint: Rust converter or neutralizer and normal paint designed for metal surfaces. 

How to Apply Paint to a Rusty Surface 

Here are several guidelines for applying paint to a rusty surface. Always read and follow the guidelines listed on your paint can – this seems simple, but it’s easily overlooked!

  1. Wear safety glasses and a dust mask – getting shards of rusty metal in the eyes is not fun. Also, you don’t want to inhale any small particles. Wear safety goggles and a properly fitted dust mask. Try to paint and prepare your surface in a well-ventilated area. Take the time to be safe.
  2. Prep the surface – this is the first step in any painting project, and it’s no different with rust. All loose flaking rust must be removed. Also, use a metal bristled brush to further clear any loose rust. If you don’t take the time to prepare your surface, your paint will soon flake away into nothing. 
  3. Use a degreaser or other cleaner – If there’s any residue on the metal surface, use the appropriate degreaser or cleaner. It’s a good practice to wash the whole surface and allow it to dry before painting. 
  4. Apply primer – depending on the surface and how long you want the paint to last, consider applying a primer before the actual paint. Many rust primers will help convert some of the rust into a stable, non-rusting compound. 
  5. Apply several coats of paint – focus on applying even, full coats. Any gaps and cracks will allow air and water to cause more rust. Apply several coats, following the paint manufacturer’s recommendations. 

These are the general guidelines for painting over rust. If you take the time to do it right, you will extend the life of the metal you’re trying to protect. 

How to Apply Rust Converter and Rust Neutralizer 

Rust neutralizer is a little different than applying regular paint. Some would say it’s easier; however, this isn’t always true. 

Here are the steps to applying a rust converter: 

  1. Choose the right product – there are rust converters and rust encapsulators. If you have heavy rust, I’d recommend using a rust converter. On the other hand, an encapsulator will do a good job isolating minor to moderate rust and prevent it from spreading. 
  2. Remember safety – wear safety goggles and a mask, and try to conduct your work in a well-ventilated area. 
  3. Prepare the surface. Unlike regular paint, you don’t need to remove all the rust. However, you should still remove any flaking rust and try to clean everything off. 
  4. Apply a thick, stable coat of rust converter. Follow manufacturer’s recommendations for how long to wait between coats. However, know that only one coat of converter is not usually sufficient. Rust is tough. You’ve got to be tougher. 
  5. Apply a protective layer  – some rust converters are sensitive to sunlight. Double-check the product you’re using and apply an outer coat if needed. 

If you take your time, you’ll save a lot of time and money in the long run. 

How to Prevent Rust After Painting 

After you’ve taken care of your rust, you’re probably wondering how to prevent further rust. Below, I’ll share a few final steps to keep your metal rust-free. 

Protect your paint from rust with these steps: 

  1. Make changes to the environment. If you’re getting lots of rust around a door, maybe there’s a gutter that isn’t working. If you have rust forming on the lawnmower, try storing it in a dry garage instead of a wet shed. Sometimes changing the environment is all you need. 
  2. Consider wax – wax will keep the paint supple and prevent it from cracking. Also, wax causes water to shed. If possible, consider using wax to slow down the rust. 
  3. Address any small problems early – If you start to see a small rust spot forming, fix it as soon as possible. Once rust has started, it doesn’t take long for it to get out of hand. Like weeds in a garden, if you nip the rust while it’s small, you’ll prevent your metal from being overrun. 

Hopefully, these tips and tricks will help you in your battle against rust.