How to Remove Rust Stains from Concrete

  • October 5, 2019
  • / By Dale Keese
Rusty Concrete Wall

When you lay down new concrete or want to take protective measures against old concrete surfaces, you need to ensure the area is clean and ready for a new layer of sealer. Concrete sealer is important for you to prevent moisture from getting into the surface and also to protect it from different weather conditions and elements. But did you know that rust can be a problem for concrete too? Before you put in a layer of sealer, however, you will need to clean out all the rust stains from the concrete so it does not solidify under the sealer and become hard to remove later. Here are some common ways of removing rust stains on concrete.

Concrete wall with rust stain

Most rust stains require some kind of acidic cleaner to remove or at least loosen the rust. The acid helps to lift the stain, making it easy to scrub away the rust stains. Most acids remove rust (a form of oxide) by converting it into an oxide that can be dissolved in water. The following are some do-it-yourself (DIY) treatments you can use to remove rust stains from the concrete.

Lemon Juice to Remove Rust Stain from Concrete

For lighter stains, a simple lemon juice is as good as any cleaner. The near concentrated form of citric acid is great for removing rust stains. Squeeze the lemon and let the juice pour all over the stain. It would be more convenient to simply use store-bought lemon concentrate instead of squeezing lemon by lemon on to the target surface. Let the lemon concentrate sit for a bit and soak in the rust. After about 10 minutes, scrub the area off with a wire brush. Rinse it out to see how much of the area has been cleared out. Repeat the process if needed.

Lemon rust stain remover

White Vinegar Rust Removal

If you are dealing with slightly tougher stains, white vinegar instead of lemon juice may work better. Simply pour the white vinegar on top of the rust-stained area and let it set. Once the vinegar has set, use a brush to scrub the rust stain out. You can also mix the vinegar with salt to increase the potency of the acid.

Carbonated Drinks to Remove Rust Stains from Concrete

Carbonated drinks can remove stains

Carbonated drinks like Coca-Cola, Pepsi, and others have an average pH of 3.4, which means they are leaning towards being an acidic liquid. The carbon mixed with the acid makes simple carbonated drinks quite effective as rust removers since they are potent enough to dissolve metal oxides. Pour the drink over the rusted area and let it sit for a bit. Then, either scrub the area out or use a power hose to rinse the area since the sugar in the carbonated drink may make the area sticky.

Hydrochloric Acid Rust Stain Remover

If the rust stain is extremely tough and you have not had any luck with any of the above DIY remedies, you can try hydrochloric acid but you have to be very careful when using this method. Do not handle the acid without proper protection such as mask and gloves. You may also want to dilute the acid slightly. Remember that when you dilute the acid, always add acid to the water and not the other way round.

This process will require you to act quickly because if the acid is left too long, the acid can stain the concrete surface and turn it into a bluish color. Let the water and acid solution sit on the rust stain for about 10 minutes, scrub immediately and then use a hose to wash the area out. This potent rust remover should be more effective when it comes to stubborn rust stains.

Remove Rust Stains from Concrete with Alkaline Stain Removers

While bases do not necessarily remove rust stains, there are some mild bases that have other useful elements that make them effective as cleaning agents.

Baking Soda

Baking soda rust stain remover

Baking soda is a mild base but is also known as an abrasive element. Baking soda is known to bubble and fizz when it reacts with certain elements. This is why it is used in cakes and baking so the crust can rise and be fluffy. When it comes to removing rust stains, the chemical reaction triggered by baking soda cuts the bond between the rust and metal, making it easier for you to remove the oxidized portions.

For this DIY project, you will need to mix the baking soda with water to make a paste so it sticks to the surface. It is important to get the consistency right. The paste needs to be thick enough so it does not become runny but also you have to make sure that it is not too grainy.

Laundry Detergent

Laundry detergent can also be an effective way to clean light rust stains from concrete. Make a paste out of laundry detergent and water and apply it to the area. If the detergent contains baking soda, the paste will become more potent. Make a paste that is thick enough so that it does not run but it should not be so crusty that it dries off too fast. Keep the DIY paste on the stain for about an hour before scrubbing it off with a stiff brush. 

Why Is Your Concrete Getting Rust Stains?

If you are noticing rust stains on your concrete more often than they should appear, check the source of your water. Often, when water comes from an underground well, the iron content in the water can be high. This iron-rich water is what could be staining not only your concrete but also any surface it may be touching, including your clothes.

Wall needing rust removal

Use a concrete sealer to prevent any damage to the surface and use a crack filler to fill any cracks that might already have occurred. You should also avoid placing any metal furniture or objects directly on the concrete. You may want to check all your pipes for any possible leaks that may be exposing your concrete surface to excess water. Constant exposure to moisture can do a whole lot of damage to concrete surfaces. The sooner you catch the leak, the better.

Something you need to keep in mind while laying the concrete is that the bars supporting the concrete should be non-corrosive. When water seeps through the concrete, the metal begins to corrode, causing the rust to emerge from within the concrete. If the metal is non-corrosive, you will not have to worry about dealing with rust from within the concrete.

Final Thoughts

Having rust stains on your concrete floor can look extremely unappealing. Getting rid of rust stains is not hard, provided you act fast and smartly. Most rust stains can be tackled with home remedies. When all else fails, there are more than enough industrial cleaners available in the market to remove such stains.

However, take note that these chemicals may be harsh so you should always wear protective tools, like gloves and masks, when dealing with acid-based cleaners like hydrochloric acid. With all these tips and tricks when it comes to removing rust stains from concrete, you surely will have no problem making your concrete look like it is brand new.