Nothing can ruin a beautiful concrete driveway, walk, or patio like rust. Rust soaks into porous concrete, leaving an ugly orange stain that can be a challenge to remove. While one’s first instinct might be to reach for common cleaning solutions such as bleach or a power washer when faced with this problem, these methods are powerless against rust.
To remove rust stains from concrete, one needs an acid-based cleaner that will dissolve the rust, returning your patio or driveway to its former glory. Rust cleaners range from common household items such as lemon juice vinegar, or a bottle of Coke, to powerful industrial cleaners like hydrochloric acid and trisodium phosphate.
This article will explore how concrete becomes stained with rust, the different methods for removing rust stains from concrete, and ways to prevent rust from staining your concrete.
- What Causes Rust Stains on Concrete?
- How to Remove Rust Stains From Concrete
- Will Pressure Washer Remove Rust Stains?
- Does Bleach Remove Rust From Concrete?
- How Do You Remove Old Rust Stains?
- How to Prevent Rust Stains From Happening
What Causes Rust Stains on Concrete?
There are several reasons why rust stains are appearing on your driveway, patio, or garage floor.
Fertilizers and Plant Foods
One common cause of rust stains in concrete that surprises many homeowners is fertilizers. Although most people know fertilizers have chemicals in them, what many don’t realize is that they also have minerals that come in the form of metals such as magnesium, iron, zinc, and even copper.
When fertilizer is applied to a yard, some of it usually ends up on the sidewalk. If it’s not rinsed away, this fertilizer can embed into the porous concrete, where it reacts with air and water to produce annoying little flecks of orange in the concrete.
Wet Tools or Furniture
Other sources can be more obvious. Rusty patio furniture, metal planters, gardening tools left out in the rain or a metal fire pit will rust onto the patio it’s sitting on, where it will soak into the concrete. These stains often aren’t noticed until after the items are moved and the homeowner finds a telltale orange outline of rust on the concrete.
Other rust stains may originate from the concrete itself. Rebar is often used in concrete construction to reinforce a wall or driveway.
While rebar won’t cause a problem as long as it stays embedded inside the concrete, if worn concrete exposes the rebar, it will interact with the air and moisture, and rust. This rust will run down concrete walls or along concrete patios or driveways when it rains, leaving an orange and unsightly trail of rust.
Even the concrete itself is a source. Some grades of concrete have metal particles in the form of ironstone or coal embedded within the rock. As the concrete wears and exposes these particles, air and moisture combine to cause rust, creating ugly orange splotches on a patio, driveway, or garage floor.
Flowing Water and Irrigation Systems
Believe it or not, your home’s water may be the culprit. Irrigation systems can carry a small amount of iron in the water in homes with hard water. When this irrigation system over sprays water onto a walk, patio, or driveway, these metal particles find their way into the concrete, where they react to the water and air, causing rust to form.
How to Remove Rust Stains From Concrete
The methods for removing rust stains from concrete are varied and many. Some involve simple items you can find around the house, such as vinegar, lemon juice, lemonade, baking soda, laundry detergent, WD-40, and even coca-cola.
While these household items can take care of milder rust stains, rust stains that have been around for a long time or are dark or widespread require a more industrial solution.
This involves industrial-strength chemicals such as oxalic acid, trisodium phosphate, hydrochloric acid, and muriatic acid. You can also use products designed specifically for rust stain removal, such as CLR.
When using industrial strength chemicals, it’s crucial that you take the proper safety precautions. This includes thick waterproof gloves to protect the hands, clothing that covers any exposed skin, safety goggles, and, in some cases, a respirator isn’t a bad idea either.
While industrial chemicals present the clearest and most present danger, even household items can be hazardous, especially when mixed with rust.
And, whatever method you choose, make sure to spot-test it before applying it to a conspicuous part of your concrete. Some methods will discolor certain types of concrete, taking an existing problem and potentially making it worse.
Apply a small amount of cleaner to a corner of concrete that is least visible, let it sit for a while, and clean it off to make sure it doesn’t leave a stain.
1. Rust Remover for ConcreteIf you don’t mind spending the money for it, this is by and far one of the easiest methods for removing rust from concrete. Unlike chemicals and household products for more general-purpose cleaners, Rust Remover for Concrete is made specifically to remove rust from concrete, whether it’s a driveway, walk, garage floor, or patio.
It does require some work to prep. The tub comes in a concentrated powder that you must mix with 1 gallon of water in a separate container before use. Once mixed, the cleaner will form a gel substance, which you then apply to the concrete by spreading it over the rust stains.
You’ll need to work diligently. Once mixed, the rust remover slowly begins losing its ability to remove rust. After four hours, it loses about half of its effectiveness, so don’t mix it until you’re ready to use it.
Once spread, let it sit for about 15 minutes, then spray the area clean with a hose. The rust should rinse away with it.
While this is an effective means of removing concrete, it can be cost-prohibitive if you’re treating a large area. A 22-ounce container of rust remover makes a gallon of cleaner, which is enough for 60 square feet.
2. Baking Soda & Laundry DetergentIf you’re looking for a method to remove rust that involves items you probably already have lying around the house, you have a few options. The first is baking soda and laundry detergent.
For this solution, you’ll need a box of baking soda, laundry detergent, a bowl to mix it in, a paintbrush and scrub brush, and a spray bottle filled with water.
Begin by mixing equal parts of laundry detergent and baking soda in enough cold water to form a pasty consistency. Use the paintbrush to spread the paste over the rust stains, completely covering the stain.
Let the paste soak into the stain for about an hour. Periodically spray the paste with water to prevent it from drying before it’s time to remove it. If the driveway or patio is hot, you may need to do this frequently to keep the paste moist.
After an hour, add enough water to allow you to scrub the stain with a brush. After scrubbing, rinse with a hose.
The baking soda creates an alkaline solution that causes rust to dissolve. The laundry detergent captures the dissolved rust, allowing you to whisk it away with a good rinse.
Given the labor involved in mixing and constantly moistening the paste, this method is best suited for minor stains instead of deep orange stains or a concrete driveway with widespread stains.
3. Vinegar and Lemon JuiceVinegar and lemon juice offers a surprisingly easy and effective way to remove stains. For this method, you’ll need lemon juice or vinegar and a wire scrub brush or a nylon brush if you’d like to take a gentler approach. To make things easier, get a large bottle of lemon juice as opposed to squeezing lemons yourself.
Begin by soaking the stain with lemon juice and allow it to sit for 10 to 15 minutes. Then go at it with the scrub brush or wire brush. The idea is to get the acid of the lemon juice or vinegar to mix with and dissolve the rust.
For tougher rust stains, you use vinegar, which is more acidic and hence better capable of dissolving that rust.
After scrubbing, rinse the concrete with a hose to remove the rust and the lemon juice or vinegar. While this method is effective for lighter rust stains, it’s impractical for widespread staining. It also won’t work as well with stains that have been around for a while.
4. CLRCLR is an excellent means for removing rust stains, along with lime and calcium deposits (hence the name), but keep in mind that, unlike Rust Remover for concrete, it isn’t specially formulated for concrete.
CLR’s listed applications include bathrooms, toilets, sinks, glass, chrome, fiberglass, stainless steel, dishwashers, showerheads, and other appliances.
That said, CLR does say on its Web site that it is safe for use on concrete. The main ingredients in CLR, which include water, lactic acid, and gluconic acid, are effective at removing rust from concrete. And CLR is somewhat safer than the harsher chemicals we’ll get into below as it does not contain harmful phosphates.
Just remember to test a small inconspicuous area to make sure it won’t stain your concrete. CLR also advises that you don’t use it on colored or tinted concrete, concrete that is less than a year old, or concrete that has been stamped, sealed, or coated.
To use CLR, create a 1-to-1 mix of CLR and water, then apply directly to the stain with a brush, cloth, or sponge. Wait two minutes, then rinse the CLR with water. With its quick-acting formula and easy application, CLR is a good option for larger stains.
5. Oxalic AcidOxalic acid is one of the time-honored methods for removing rust stains from concrete, but it can be difficult to find. Some big-box stores sell oxalic acid in its powdered form, and some specialty paint stores also sell it as it’s effective for bleaching wood.
You’ll need a bucket, mop, and scrub brush for this method. To use the powdered form of oxalic acid, mix half a cup of powder with a gallon of warm water. As with other acids, only mix in a glass container or plastic container that is acid-resistant.
Apply the solution to the stains using a mop. Allow the solution to work into the stain for 5 to 10 minutes, being sure not to let the area dry.
Next, scrub the stain with a scrub brush. Remembering this is a type of acid, so taking the necessary precautions mentioned above is critical to using this product safely. After scrubbing, rinse with water. If the stain is still present, treat it again.
If you aren’t able to find powdered oxalic acid, you can also find it in certain industrial cleaners sold at most big box home improvement stores.
6. Trisodium PhosphateAnother industrial strength product that is effective for cleaning rust stains is trisodium phosphate. The chemical, commonly found at most home improvement stores, will break down rust, allowing you to rinse it away.
To use TSP, you’ll need proactive gear as it will burn skin and eyes on contact, a scrub brush, and a bucket for mixing. Begin by mixing half a cup of TSP with half a gallon of hot water.
Pour the mixture on the rust stains and let sit for 20 minutes. Use a nylon brush to scrub the stains in a circular motion. This will ensure the TSP comes into contact with all of the rust particles. Rinse afterward. If the stain isn’t completely gone, reapply.
Methods such as TSP are one of the most effective ways of removing stubborn rust stains, and TSP is also useful for other applications.
7. Hydrochloric AcidWhen it comes to removing tough rust stains, few methods can top the power of hydrochloric acid. This chemical is so acidic that it effectively disintegrates rust.
Just keep in mind that rust isn’t the only thing it will disintegrate. It’s one of the most dangerous chemicals for removing rust and thus should only be used with an abundance of caution and as a last resort. Gloves, goggles, and clothes that cover exposed skin are an absolute must.
Begin by mixing two parts hydrochloric acid with one part water. Apply the mixture to the stain and let sit for up to 10 minutes.
Do not leave the acid on the concrete for more than 10 minutes. Doing so can cause the concrete to turn blue, creating a whole new type of stain to contend with. Scrub the rust away using a scrub brush, then rinse the surface with water.
Apply a second treatment if the stain persists after the first round.
8. Simple Green Pro Heavy Duty CleanerThe nice thing about this Heavy Duty Cleaner is, like Rust Remover for Concrete, it’s designed for use on concrete. It’s also sort of an all-purpose driveway cleaner, so not only will it remove rust, but it will also take care of other common stains you’d find on a driveway or garage floor, including stains from grease, oil, and exhaust.
This product is safer than other options and is also great for treating large areas, like an entire driveway or patio, as it can be applied with a spray bottle or even a pressure washer.
The product comes in concentrated form, so you’ll need to begin by mixing one cup of cleaner with one gallon of water. Spray the stained area, then let sit for five minutes. Scrub the area with a stiff brush or push-style broom to move the rust particles, then rinse it away with a hose or sprayer.
9. Muriatic AcidBy this point, you might be noticing a trend here. Strong acids remove rust, which is why so many of them are on this list. purchase acetone is another strong acid solution that can be purchased at most big box home improvement stores. It’s cheap and effective, but it’s also dangerous, so make sure to use plenty of precautions when using it.
As with other acids, muriatic acid should be diluted before use and mixed in a glass or acid-resistant container.
Mix one part acid with 10 parts water, being sure to pour the acid into the water to prevent splashing a high concentration of acid. Spray or brush the acid onto a stained area and allow it to sit for up to 10 minutes.
As with hydrochloric acids, muriatic acid can stain concrete if allowed to sit for longer. Clean it with a solution of baking soda and water. The baking soda will neutralize the acid.
10. Coca-Cola or LemonadeIt may seem odd to think something as innocuous as Coca-Cola or lemonade is powerful enough to remove rust stains, especially compared to something as caustic as muriatic acid, but it is. That’s because both beverages have the main ingredient needed to dissolve rust, acid.
The application is simple. Begin by pouring undiluted Coca-Cola or lemonade on the rust and let sit for 15 minutes to allow the acid to soak into the rust stain. Use the scrubber brush to work the Coca-Cola or lemonade into the stain until it’s gone, then rinse with water.
While neither beverage is as strong as some of the industrial acids on this list and neither is practical for larger treatments, such as an entire driveway, this method is a quick way to get rid of relatively minor rust stains
11. WD 40This lubricant and cleaner is something most homeowners have in their workshop. Just as it’s effective at cleaning rusty off tools, it’s also effective for getting the rust out of concrete.
The application is simple. Spray the WD-40 directly on the rust stain, then scrub with a brush.
The WD-40 will penetrate and get under the rust, working it free from the concrete. Reapply if needed to completely remove the stain.
Once satisfied, rinse the area with a hose to clean the area.
Will Pressure Washer Remove Rust Stains?
Generally speaking, pressure washers are not an effective means of removing rust stains. This is because rust stains penetrate the concrete and pressure washers typically only remove dirt and grime that is on the surface.
That said, pressure washers can be effective when used with the right cleaners. Typically this involves soaking the surface with a cleaner that brings the rust to the surface, then using a pressure washer to rinse the cleaner and rust off the surface.
Does Bleach Remove Rust From Concrete?
While bleach is a powerful cleaner capable of combating many things, rust isn’t one of them. Chlorine simply isn’t the right chemical for removing rust. Attempting to remove rust with chlorine can cause more discoloration, making the stain worse. Leave the bleach for cleaning mold and mildew and use an acid-based cleaner for removing rust.
How Do You Remove Old Rust Stains?
Rust stains on concrete are bad enough. Stains that have been on concrete for a long time can be a real pain. This rust has had time to soak deep into the porous concrete, making it difficult to remove.
For dark old rust stains, don’t waste your time with home remedies such as lemon juice and vinegar. You need a much stronger acid. Strap on the protective gear and use hydrochloric acid if you can get your hands on it, or muriatic or oxalic acid if you can’t. Specialty products such as Rust Remover for Concrete are also a good option.
When battling dark old rust stains, keep in mind that it may take several treatments to completely remove the stain.
Don’t get discouraged. Keep at it to remove the stain, then be sure to eliminate the source to prevent it from reemerging later.
How to Prevent Rust Stains From Happening
The old saying an ounce of prevention is worth a pound of cure is certainly true for rust stains.
Certainly, the easiest way to solve a rust problem on a concrete patio, driveway, or garage floor is to prevent the rust stain from happening in the first place.
One way is to minimize the contact your concrete has with metal. This means removing or covering metal patio furniture when not used to prevent it from coming into contact with rain and rusting. Don’t leave metal lawn tools on a concrete patio or driveway.
Both are good practices not just for preventing rust on a patio or driveway but also for ensuring your yard tools and patio furniture have a long life.
In a garage, make sure not to leave any damp or wet metal tools lying on the floor.
If possible, prevent large amounts of water that can carry small amounts of metal in them from draining through a patio or driveway. When irrigating a lawn, make sure to limit overspray on these areas.
If it’s in your budget, the best way to remove stains from concrete is by using a cleaner specially designed for that purpose, such as Rust Remover for Concrete or Green Oxy Solve Concrete. For tough stains, use a powerful acid, such as hydrochloric acid or muriatic acid.
Lighter stains can be taken care of with home solutions, such as lemon juice vinegar, baking soda, and even a can of Coca-Cola.
Whatever solution you choose, be sure to use the proper safety precautions when cleaning rust from concrete, including gloves, eye protection, and coverings for exposed skin.