Can You Paint Rustoleum Over Ospho? (Explained)

Rustoleum and Ospho are popular rust treatments and protective coatings. Ospho has a duller finish. It’s why you may consider painting Rustoleum over it.

This article will address whether it’s okay to paint Rustoleum over Ospho and anything else you may need to know about these two protective coatings.


Let’s Start by Introducing Ospho

Unlike Rustoleum, Ospho isn’t as famous. It is a two-part phosphoric acid etching process that restores rusty metals. It is an effective yet affordable solution that cleans out dirt and corrosion.

Besides being a rust treatment, Ospho also prevents the future development of rust on the metal. It is effortless to apply. You don’t need to sand the surface. Just clean and spray it on.

What about Rustoleum?

If you own a car or interact with things that contain metal, such as bikes or wheelbarrows, Rustoleum should be a familiar name. This paint and primer can be sprayed on rusty surfaces to treat and prevent further corrosion.

It’s just like Ospho, only that it is available in a wide range of aesthetically pleasing finishes. That is why most people consider painting it over Ospho’s dull finish.


Can Ospho Be Painted?

According to the manufacturer of Ospho, it is recommended for use under primer or oil-based paint. They also explain that Ospho creates a strong bond between rusted metal and paint. Therefore, Ospho can be painted over. But can you use Rustoleum?

Can You Paint Rustoleum Over Ospho?

Yes, you can paint Rustoleum over Ospho. However, there is one main limitation which we will discuss below.

Ospho, as mentioned earlier, is one of the best rust treatments. When applied to rusty metal, it interacts with the iron oxide forcing it to turn black or dark blue.

Unlike Rustoleum, Ospho is not a primer, and neither is it a paint. It is strictly a rust treatment. Therefore, its job is not to enhance the beauty of the rusted piece.

Even though Ospho looks hideous once it has cured on the rusted metal, it can be painted, and that’s where Rustoleum comes in.

If you want to improve the look of the rusted metal, you can paint it with some Rustoleum to get a much better finish.

Most professionals have an issue with painting Rustoleum over Ospho because the former is also a rust treatment.

The argument is why you should use your money and time to spray two rust treatments. Isn’t it better to use Rustoleum and get the rust treatment, protection, and a better finish?

The decision to use Rustoleum over Ospho depends on your preferences and objectives. I am just here to clarify the purpose of using both Rustoleum and Ospho.

When used together, you will enjoy peace of mind knowing that you have a double rust treatment on the metal. However, on its own, Rustoleum is powerful enough to deal with rust and prevent it from occurring in the future.

Unless you feel the urge to use both Ospho and Rustoleum, only one of these is enough to deal with rust. The only exception when it makes sense to use two treatments is if the object is extremely rusty.

Regarding painting over Ospho, you can use any other type of paint you want over this rust treatment. Ospho doesn’t limit you to the kind of paint you can or can’t use as long as you spray down a primer first to promote adhesion.

How Do You Paint Rustoleum over Ospho?

If the metal piece has been treated with Ospho and you want to paint Rustoleum over it, here is how you can go about it.

Spraying Rustoleum over Ospho is pretty straightforward. You first need to let the Ospho dry if it has been painted recently. Then clean off the flakes with a wire brush.

After that, it can be tempting to skip the primer application, but this is mandatory. Spray primer and then Rustoleum.

Give it time to dry, and now you will have two rust-protective coatings and a better finish. You can touch up the Rustoleum occasionally if it starts to wear out.

Do You Need to Sand Over Ospho Before Painting Rustoleum?

As long as you use a primer, there is no need for sanding over Ospho. Sanding is crucial in promoting adhesion and getting rid of rust from metal.

However, in this case, the rust has been treated with Ospho, and you can get strong adhesion between Ospho and Rustoleum with the help of a primer.

Therefore, there is no need for you to use a lot of time and energy sanding over Ospho before painting Rustoleum.

How Long Does Rustoleum Last Over Ospho?

Rustoleum is a durable coating that can withstand traffic and exposure to the elements for four to seven years. As long as the surface treated with Ospho is well prepared, and the Rustoleum is applied correctly, it can last for more than five years.

It will need to be touched up occasionally. However, Rustoleum should serve you for an incredibly long time before it needs to be re-sprayed.

Will Ospho Bleed through Rustoleum?

Considering that these are two different rust treatments and one contains phosphoric acid, it’s understandable that you may be worried about the Ospho bleeding out through the Rustoleum. If this were to happen, it would be an epic failure.

Even though Ospho contains phosphoric acid, it will not bleed through Rustoleum when you let it dry first.

The main reason Ospho can bleed through Rustoleum is when you spray the latter before the Ospho cures. Doing so may fail because the phosphoric acid is still active.

Ospho dries overnight. But it’s a good idea to let it sit for 24 hours. Only after this period has lapsed, then can you spray Rustoleum. It’s advisable not to rush this project.

Can You Apply Ospho Over Rustoleum?

Now that you have figured out that it’s okay to paint Rustoleum over Ospho, how about vice versa? Will Ospho stick to Rustoleum?

First, you will be going against the manufacturer’s recommendations. Ospho goes under and not over the paint. Therefore, using it over a paint such as Rustoleum may not stick for long.

I would advise you to refrain from using Ospho over Rustoleum. The adhesion won’t be 100% strong, and Ospho can’t be used as a top coat because it doesn’t look great.

Unless you don’t care about the aesthetics of whatever you are treating with Ospho, never use it as the final coat.

Does Ospho Need to Be Complemented with Another Rust Treatment?

Sometimes, Ospho may leave behind rust spots that need to be converted with another rust treatment. If a piece is extremely rusty, you may need to combine it with another treatment such as Rustoleum.

If you think a particular object is too rusty to be treated with only Ospho, feel free to bring in the big guns.

What Types of Paint Can You Use Over Ospho?

Being a paintable surface, you can use any automotive paint. It all depends on the quality of finish you would like to get. If Ospho has been used on a car, you can use automotive paint and finish it with a clear coat for a much better finish.

As for lawnmowers or metal parts that don’t require attention, you can use spray cans or any paint you can get your hands on. Alternatively, you can leave the Ospho as it is because it will prevent further corrosion.

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