You might want to paint over your rusted metal or any other rusted surface to stop the rust from spreading. It’s a way out many have already applied. But there are a few considering facts that will make you question – will painting over rust stop it? And, of course, to what extent?
Painting can stop rust from spreading, but it depends on the rust condition, the types of paint used, and the application of paint. Before you get yourself busy with the process, get the basics clear.
Rust is the result of the reaction between alloys of iron with moisture. Iron oxide could also form due to water constantly running over steel. Now that you know iron reacts with moisture, covering the steel up with a protective layer is the solution.
Rusting is a continuous process, and outer moisture speeds it up. However, it’s mentionable that water alone cannot cause rust. By moisture, we mean the combo of both water and air.
Surprisingly, among many other coatings, paint has always been an easy pick for the job.
Why Should You Paint over Rust?
Painting over rusty metal could be a winning game for you, saving you a lot of money rather than replacing the metal.
For a rough idea – 12 ounces of paint can cover 15 sq. ft. So, with 12 ounces of paint and 12 ounces of primer, a small portion of a table will cost you around $8. Whereas scrapping and replacing the barebones of a metal table will get $25 out of your pocket.
So, you are saving almost $17 for a small project, and it will climb more for larger projects.
Does Painting over Rust Stop Rusting?
Paint layers aren’t permeable, and moisture cannot pass them. Whenever we are providing a paint layer, a barrier is created between the iron and the water content. Hence, the continuous rusting process is disrupted.
How Can Painting Stop Rust from Spreading?
After the barrier is created, further contact between iron and moisture is stopped, and no new rust will form.
However, how the rust under the paint will react is still a question.
Types of Paint That Acts Against Rust
There are two types of paint for fighting rust:
- Paint for Rust Prevention
- Paint for Rust Neutralization
The first one includes the removal of the rust from the exterior and applying a protective paint layer for further protection. However, the second one is a hassle-free tool.
Rust prevention paint needs preparation like removal of rust and application of primer. This type of paint is used for projects where color is an unavoidable feature, like doors and chairs of metal.
You can directly use this paint over the rust as it actively reacts with the rust. As a result, you got a stable layer over the rusted metal. Removal of rust isn’t necessary here (except the flaky ones).
Unlike rust preventing paint, you will use this rust converting paint for projects where color isn’t a considerable feature, like a car’s underside.
However, you can choose to paint over a rust neutralizer as well.
- Rustoleum – It’s a conventional paint that can be used for rust prevention.
- POR 15 – It’s a rust neutralizer, also called a rust converter.
- Corroseal – It’s a rust converter that is non-sensitive to direct sun.
Does Spray Paint Works over Rust?
Covering up the rust with spray paint might seem an easy and aggressive approach, but it’s temporary. Suppose you have given full coverage to the rust and stopped the moisture contact. Now you will not witness any rust on the surface layer.
Unfortunately, the rust might spread even under the paint if the situation is worse. Without even a sign on the outer exterior, the rust is corroding the structural integrity of the iron progressively.
You can eventually stop this widespread rust underneath the painting. Follow the steps of cleaning and brushing away the rust. Then it will be followed by primer application. At last, you are ready to spray paint.
What You Should Consider Before Painting over Rust?
Will painting stop widespread rusting or not is solely connected to the way you paint, considering some factors –
To What Extent the Rust Has Spread
When the rust is only on the exterior, the paint can deal with it. If you are witnessing holes and pits on the metal, it means the metal has been weakened structurally.
At this point, the metal has become so fragile that you can even bend it with your bare hands. So, painting on such a metal is not only useless but also a waste of paint.
The widespread of holes might be severe or partial. In case of partial damage, filling those holes using an auto body filler might restore the metal. The other alternative is to replace the metal.
A good body filler could be Bondo.
Consider Removal of the Rust
Here, we are talking about those loose rust that tends to shed off from time to time. Painting or even priming over loose rust will detach the dried paints from the base and blister.
Step 01: To remove those loose rust, you need to sand the surface or run over it using a wire brush. Don’t be too harsh, and remove as much loose rust as you can.
Step 02: After you got a clean surface free from any rust flakes, time to get rid of grease and grit. Use any preferable degreasing solution for the job. A homemade one will work as well.
Damp a rag with the solution and wipe over the surface, followed by a final swab.
As for the homemade mixture – mix four teaspoon of dish liquid with a gallon of water. Finally, air-dry the metal.
Right after you get rid of loose rust, there are possibly two conditions that you will see – extensive surface rust or almost no rust.
The good thing is that you can deal with both, but paint alone won’t be enough. Paint can’t adhere to rusted metal even if it’s rusted in the slightest amount. In this situation, priming not only solves the problem but also creates a better base for the paint.
Now, you might be thinking about some scenarios where you saw paint sticking over rusted metal.
Very important info to mention – such metals have high chances to discolor as rust stains eventually bleed through the coat and show off on the exterior.
Prime right after cleaning the surface, or there will be room for further reaction between metal and moisture. Avoid applying multiple layers of primer at a time. Wait for the recommended time for each layer to dry.
Rust-oleum Metal Primer is a good choice for the job.
Choosing between Oil-Based and Water-Based Paint
As said above, rust is the corrosion of metal due to exposure to moisture. Water-based paint has water in the formulae. In case you are not considering priming, direct application of water-based paint might get you to square one.
After some time, you might notice the presence of rust again. So, consider using an oil-based primer first. Even if it’s highly recommended, it’s not mandatory to use primer while using oil-based paint.
When Should You Avoid Painting over Rust?
Even if the technique works, you need to know how much the metal has been affected. Rusting of a metal refers to corrosion.
In the process of removing the rusted part before painting, you will end up removing major parts of the metal if it’s too much or wholly rusted.
Moreover, there might be other factors that will hinder you from painting. Depending upon the use of that metal, you might need to think over whether or not you will paint it.
How to Prevent Rust After Painting?
Some steps might save your metal from further rusting.
Early Acknowledgement of Any Issue
Just like the weed on the lawn, rust doesn’t take time to get out of hand. So, whenever you spot rust, act immediately, regardless of how small it is.
Change of Pace
Sometimes the surrounding environment is the root of all evil. If any of your metal gets too must rust within a small period, change its storing environment. Like a lawnmower can rust if left in a damp garage. So, try storing it in a dry space.
Now you know – when will painting over rust stop it, and what is the procedure. Paint can not only stop further rusting but also help you get a new look. Certain metal equipment gets in touch with water every day, depending upon its use.
Such metals need coating even before its rusted. Here, we discussed the possible solution to tackle the rust that has already been formed.
Painting over rust without getting rid of the flaky ones will blister the dried paints. However, the rust formation will slow down if you prepare the surface by cleaning and priming.
It’s worth painting over rust if you know when to paint. You will paint when the rust is limited to the surface. If the metal’s internal structure has been affected, you better rethink it.
It’s indeed ok to paint over a rusted metal surface. But how long the paint will last solely depend on the application procedure. Preparing the surface before painting is what will regulate the output.