Before painting any surface it is always important to prepare it first. That means cleaning it and priming it for the new paint. This is especially important when painting metal. In this article, you learn exactly how to properly prepare any metal surface for painting and you will learn what materials you can use to do so and which materials you should better avoid using.
As a whole, to prepare metal for painting the metal surface has to be cleaned from any dust or debris. Old paint and rust should be removed from the surface and any holes, cracks or dents have to be fixed. And finally, a primer should be applied to the surface before applying the paint.
That’s basically all you have to do to prepare a metal surface for painting. Don´t worry I will explain each of these steps in detail in this article.
The Four Steps to Prepare Metal for Painting
Before painting any kind of metal surface you should always go through each of these steps. If you determine that one step is not necessary then simply skip it and look at the next one.
The only two steps that you should never skip no matter what, are cleaning your surface and priming the surface. Some paints don’t require you to prime the surface in which case you could skip that step but I generally recommend always priming your metal surface before you paint it even if the paint doesn´t necessarily need a primer.
Clean the Surface Roughly From Dirt and Dust
You should never skip this step no matter if the surface of the metal is clean or rusty. Before doing anything you should always clean the surface roughly.
I usually use a simple sturdy brush and a piece of cloth or a towel for cleaning.
You don´t need to clean the surface perfectly yet and you won´t need mineral spirits yet. We will clean the surface again before applying the primer. In this step, we only want to get rid of dirt and dust.
Use the brush to clean the surface of the metal from dirt, spider webs, and dust. Then use the towel or a piece of cloth with some water to get rid of any dirt and dust that´s leftover. The surface doesn´t have to be perfectly clean yet.
Remove Peeling Paint and Sand if Necessary
As a general rule, it is only necessary to sand metal before painting if the metal surface has rust, paint, or something similar on it that needs to be removed. The metal surface does not need to be sanded if it has oil, grease, or dust on it as this can easily be removed by using mineral spirits.
If the metal was already painted before and the paint is peeling or bubbling then you should remove the paint.
If the metal was painted previously but the paint is not peeling then you can leave the paint where it is and simply continue with the next step.
You have to remove any peeling paint before you can repaint the surface. I recommend doing that either by using a wire brush to scrape the paint off or by sanding the surface.
You can buy a wire brush in your local hardware store or right here on Amazon.
I personally always do both.
I usually start by using a wire brush to remove any paint that is easily peeling of and to remove some of the rust, if present. And then I will go over the whole piece with fine-grit sandpaper.
Try to be careful when using a wire brush. You don´t want to damage the metal underneath.
Then, when most of the paint and the rust are removed, I will go over the entire piece with a fine-grit sandpaper. 100 girt is usually good enough.
You should remove all of the rust and paint before going to the next step. This is by far the step that will require the most work but it will be worth it because by doing this you will ensure the longevity of the new paint job.
Clean the Surface With Mineral Spirits
As I said above, this step should not be skipped no matter what. Even if your metal is clean and no rust is present before you apply any paint or primer you should clean the surface from grease and dust.
If you don´t clean your surface properly then you might have a problem with peeling paint later on!
Use a piece of cloth or a towel to wipe the surface with some mineral spirits. This will clean the surface from any oil or grease that might be left on the surface. You might need to change the towel after a while if the surface was very greasy.
Finally, after you cleaned the surface properly, use a rust reformer before painting the surface to ensure that no rust can build underneath the paint coat.
Some primers nowadays already stop rust from building anyways but I generally recommend applying a rust reformer anyway just to be sure.
I personally recommend using the rust reformer from Rust-Oleum. It is easy to apply and it never failed me. You can buy Rust-Oleum rust reformer at your local hardware store or right here on Amazon.
Usually a thin coat of rust reformer will be enough in most cases.
Prime the Surface if Necessarry
Applying a primer is not really necessary anymore nowadays. At least in most cases.
Most modern metal paints will stick to the metal without the need for a primer and even the rust reformer from Rust-Oleum that I recommended before states that it will create a paintable surface.
I still recommend applying a primer before you paint a metal surface just to be sure. A dedicated primer will prepare any metal surface for paint application and it will sometimes adhere slightly better than most paints that can be painted directly to metal.
My favorite primer is the spray primer from Rust-Oleum. You can easily apply it and the result is always very even. Rust-Oleum spray primer can be bought at your local hardware store or right here on Amazon.
How to Prepare Rusted Metal for Painting
Sometimes you may have to deal with really rusty metal that you want to give a new life or just a new coat of paint but how can you go about this? Well, it´s pretty much the same as with any regular piece of metal with one exception. You might need to fix some holes, cracks, or dents.
As a whole, to prepare rusted metal for painting it’s necessary to remove the rust first. This is usually done by using a wire brush and sandpaper. If there are holes, cracks, or dents in the metal then some epoxy filler should be used to fix them. Finally, a rust reformer has to be applied before painting.
As you can see it’s not that different from preparing any other metal surface for painting.
We still clean our metal surface and then remove old paint and rust with a wire brush and sandpaper.
But then we will fix cracks, dents, or holes that might have been caused by the rust. This is really the only big change from regularly preparing a metal surface.
We will fix these imperfections by using something called “epoxy filler”. This is a two-component mass. As soon as you combine the two components, the hardener, and the epoxy, it will start to harden.
But don´t worry. You have more than enough time to apply it to the metal surface before it fully cures.
The epoxy filler has a consistency similar to dough. Once applied let it harden for a few hours.
You can sand the epoxy to smooth it before you apply the primer.
You can get epoxy filler at your local hardware store or right here on Amazon.
Finally, all that’s left to do is applying a rust reformer and a primer. A rust reformer is very important here to ensure that any rust, that might still be leftover, is being reformed. This will basically make sure that no rust will build under the coat of paint.
Solutions That Can be Used for Cleaning Metal
When it comes to cleaning metal for painting my recommendation is always mineral spirits but there are a few alternatives that can work and there are a few that you should not use.
As a whole, rubbing alcohol as well as a vinegar and water mixture can be used to clean metal before painting it. Paint thinner, on the other hand, should not be used to clean metal to prepare it for painting. Paint thinner will leave some residue on the surface that will hinder paint adhesion.