It’s undeniable that concrete surfaces add to an environment’s aesthetic value. However, that comes at a price. Since concrete surfaces come from “soft rock,” concrete slabs, driveways, and sidewalks are prone to have rust spots. The spots resemble metal sticking out, forming a darker color over time.
Rust spots are a common eyesore for most homeowners. Nobody wants ugly, rusty, and degraded concrete surfaces. Stained concrete surfaces leave houses, sidewalks, and driveways looking bad hence the need to remove them. Here’s how to remove rust from concrete in 9 steps.
Step 1: Identify the Source of the Rust
Before attempting to remove rust stains from your concrete, you must first determine the underlying cause of the problem. If you don’t get rid of the source of the problem, the stains will most likely come back, and your maintenance work will have been for nothing.
While there are obvious sources of rust on surfaces, it’s also possible for rust to originate from the concrete itself. If moisture and air react on the concrete’s mesh, cracks form, resulting in damage. The cracks allow rust to form under the floor and reach the top of the concrete surface.
The biggest source of rust is iron stone and coal (soft rock) within the concrete.
The soft rock absorbs much water exposed to chemical reactions with the iron component through oxidation. Eventually, the exposed surface rusts form red, then dark orange defects on sidewalks and concrete walls. Once absorbed into the concrete pores, the rust becomes challenging to eradicate.
Oil and grease stains cause rusting, especially on driveways. For instance, spillage in your vehicle causes dark gray or black pigments that track to the source. Since concrete is porous, it slowly penetrates deep into layers to form rust.
Step 2: Choose the Right Cleaning Solution
Unlike food or dirt stains, removing rust spots using regular detergents or water is impossible. You’ll need to get acid-based cleaners to dissolve the rust. The stain’s age, its severity, and the concrete surface’s porousness will dictate the best substance to use.
The earlier you treat the rust stain, the easier it’ll be to get rid of. Organic acidic cleaners are typically effective in removing new stains that aren’t deep into the concrete.
The most common domestic cleaners include lemon juice, baking powder, and white vinegar. White vinegar is more acidic than lemon juice. Thus, it’s more effective on resistant rust spots. Here’s how to remove rust on concrete surfaces using lemon juice and vinegar:
- Start by cleaning the floors for the acid to penetrate fully
- Next, pour the liquid onto the stained surfaces and allow it to sit for 10 minutes
- Scrub the stains away with a stiff-bristled brush or scraper
- Finish by rinsing with warm soapy water
If you use baking powder, use a soft brush to spread the paste on the stained surface and let it sit for an hour or so. Then, use a brush to scrub the paste and remove the rust. Finish by rinsing the paste with water and repeat the process if necessary to achieve thorough results.
If you can’t find domestic solutions, you may use commercial cleaners to clean rusty surfaces. Some commercial cleaners contain oxalic acid that removes even the toughest stains.
You’ll need to follow the manufacturer’s directions for the best results. Hydrochloric acid and trisodium phosphate might also remove concrete rust. However, hydrochloric acid turns concrete blue if left on for too long.
You should also wear gloves, safety goggles, and gumboots while working with commercial cleaners. Besides removing rust stains, these chemicals may also dissolve coatings and concrete stains, so you may need to perform some touch-up work afterward.
White vinegar is cheap and readily available. It’s also a safe and reliable cleaning agent that cleans kitchen appliances, garages, and driveways. However, saturating concrete for too long in vinegar damages the cement that binds the concrete, causing erosion.
When using vinegar on unfinished concrete, let it sit for 15 minutes. In addition, white vinegar doesn’t smell good during cleaning. Mixing lemon juice and vinegar during cleaning is recommendable for a more pleasant smell. A 1:1 ratio is recommendable.
Baking powder is mildly abrasive, which is ideal for cleaning rough surfaces. When mixed with water, the baking powder works as a degreaser by dissolving grime and grease. Although it won’t damage concrete, it isn’t very pleasant on the skin and can cause burns. It also causes surface voids and pinholes.
Like other domestic cleaners, lemon juice is an excellent concrete surface cleaner. It’s also a natural antiseptic and antibacterial bleaching agent. Lemons have an amazing citrus scent that is refreshing and energizing. However, it’s corrosive on brass-plated surfaces.
Commercial concrete cleaners improve concrete’s appearance by giving it a new, cleaner look. Commercial cleaners also extend the lifespan of concrete surfaces through pressure washing. They also reduce debris and dust on concrete surfaces.
Most commercial cleaners are all-purpose cleaners. You can use them on sidewalks, driveways, bathrooms, kitchen surfaces, and walls.
However, commercial cleaning agents contain chemicals such as ammonia or bleach that are dangerous to your health. They’re also known to have hazardous environmental effects. It’s essential to take precautions when handling them and follow instructions.
CLR (calcium, lime, and rust) is another common commercial concrete floor cleaner. It’s safe, reliable, and readily available in hardware stores. Since it’s rich in gluconic and lactic acid, it’s less harsh and cleans faster than other acid-based cleaners.
Nevertheless, it’s advisable to follow the manufacturer’s instructions. They advise against use on colored or newly installed surfaces. Test CLR before applying it on your surfaces to avoid any adverse outcomes.
While hydrochloric acid is the most effective chemical for removing rust stains from concrete, it also poses a significant health risk. The acid tends to burn everything it comes into contact with.
Wear gloves and safety goggles to keep your eyes and hands safe. Then, dilute acid with water at a ratio of 1:2. Mix up and apply to the stained area gently. That will take a short time, so come back after ten minutes. If you let it sit longer, your concrete will develop fresh stains. Scrub, then carefully rinse off.
Persistent stains call for the strongest acids and chemicals. In such situations, trained professionals using specialized equipment will produce the best results. Muriatic acid works better with stubborn stains. You’ll need to combine this with a lot of water (1:10).
Trisodium phosphate might also help with such stains. Prepare a mixture of half a cup of the formula and half a gallon of water.
Step 3: Gather the Necessary Tools
Manual cleaning techniques such as mopping are tiring and a waste of time when cleaning concrete surfaces. Furthermore, they don’t deliver the desired result in terms of cleanliness. Thus, more advanced cleaning machines do come in handy. They include;
- Pressure washers
- Floor scrapers
- Stiff-bristled brushes
- Protective gear
Pressure washers are a must-have- tool used to clean concrete surfaces. However, there are some features to consider when purchasing a pressure washer. Pressure washers come in different PSI levels (pounds per square inch).
For basic cleaning tasks such as sidewalk cleaning, a small washer with a PSI of 1,000 to 1,900 is appropriate. However, more technical jobs like concrete cleaning require a PSI of 3,200 to 3,800.
It would be best to consider portability, though it usually depends on the size of the area you’re working on. You can settle for an electric washer if you’re working in a smaller space. Consequently, working on larger areas requires a more portal washer. A gas or diesel washer is ideal for such scenarios since it allows you to move while using the machine.
Since pressure washers exist in many models, some come standalone with no additives, while others come with attachments. The power broom attachment is essential for cleaning larger areas such as driveways. The turbo nozzle uses a high-pressure rotating jet formulated to scrub away grime and cut cleaning time.
Floor scraper removes concrete surfaces’ build-up and residue without damaging them. They’re available in light, medium, or heavy-duty scrapers. Light-duty scrappers remove wax, tough dirt, gum, or stickers.
Medium-duty floor scrapers are used in industries to remove industrial scraping, tape, and push heavy dirt. Heavy-duty scrapers remove adhesives, carpets, and strip floor tiles.
You can use a stiff-bristled brush for heavy cleaning tasks such as driveways, brickwork, and wood decking. The brush usually has two spray jets that fit into multi-link adaptors and water poles.
Safety is paramount when working on concrete surfaces, especially with commercial cleaning agents. Concrete protective gears such as boots and gloves prevent the chemicals from causing skin irritation or burns. They also protect the skin from abrasions.
Safety goggles prevent eye irritation from dust and chemicals. It would help if you went for shatterproof goggles that resist heavy impacts. Face masks help prevent lung problems caused by concrete dust.
You’ll also want to have an apron to cover your whole body. That reduces the risk of skin irritation and concrete burns. Most commercial cleaners’ producers warn against utilizing their products inside closed spaces.
Step 4: Prep the Surface
Surface prep entails cleaning concrete surfaces in readiness for new coatings. For most surfaces, it’s vital to remove old coatings because if you apply new coats to existing ones, peeling or flaking will continue under the new layers.
Because of their acidic nature, certain concrete rust cleaners pose a risk to nearby plants and surfaces. Covering any nearby plants before applying any remover is a good idea.
In addition, eliminating old coatings prevents corrosion and lengthens your concrete surface’s lifespan. Before applying new coatings, consider removing loose surfaces.
Surface preparation helps save money by reducing the risks of costly reworks in the future. Unprepared concrete surfaces can manifest immediately after installation.
However, proper preparation ensures an effective substrate bond. Surface preparation extends to the floor’s durability, strength, appearance and reduces the possibility of coating failures.
Step 5: Apply the Cleaning Solution
Start by cleaning the concrete surface with soap and water to wash away surface-level dirt or grease. After the surface is clean, use a domestic or commercial cleaner, depending on the nature of the rust spot. Next, apply the rust remover or acid of your liking on the rust spot.
Let it sit for approximately five to ten minutes, then scrub the rust spot and rinse with soapy water. Make sure to use an appropriate brush for the concrete to avoid damaging it. Repeat the process for desired outcomes and use a pressure washer for stubborn spots.
Whether you’re dealing with minor or stubborn rust stains will dictate the right concentration of the cleaning solution. A solution’s concentration will impact its effectiveness. It might not be powerful enough to remove the stains if it’s too low. Similarly, an excessive concentration may end up damaging your concrete.
Furthermore, you’ll need to use the proper concentration for safety reasons. Too much of it can be harmful to handle and irritate the skin and eyes.
Step 6: Scrub the Stain
After allowing the cleaning agent to sit on a rust spot for 10 to 15 minutes, use a hose and wet the surface. Scrub the surface using a bristled or firm brush and a water solution with a cleaning agent. Depending on the rust stain, you might need a pressure washer.
Firm pressure is effective and helps you save money. Besides rust removal, it helps remove mold, build-ups on surfaces, dirt, and dust particles. Using firm pressure guarantees the cleaning solution goes deeper into the rust stain. That improves its efficiency and ensures that the rust stain disappears entirely.
Step 7: Rinse the Surface
After scrubbing, complete the cleaning with a good rinse by thoroughly removing the cleaning agent and soapy residue. Next, allow the concrete to air dry. Once you remove a rust spot, you’ll notice a discolored spot. To remedy the situation, use concrete resurfacing or coloring that is rust-preventive.
A pressure washer is eco-friendly and efficient as pressurized water removes rust from metal surfaces. It also utilizes mild and effective chemicals to remove tough stains. The method is safer than other chemicals that are harmful to aquatic environments.
The time and energy necessary to clean a bigger space is a lot. Furthermore, hiring an expert to do it for you can be pricey. Pressure washing allows you to avoid spending money on labor and cleaning.
Pressure washing is safe in comparison to sanding and grinding. They increase the risk of skin injuries and respiratory diseases due to concrete dust and rust.
Step 8: Repeat as Necessary
Ensure to clean interior surfaces at least once every two weeks or whenever dirt builds up. It is a good idea to clean exterior surfaces once a year, while you should do stain removal when necessary.
Always choose the least toxic cleaners to remove rust on concrete surfaces. You should only use toxic cleaners if it’s unavoidable. Finally, inspect floors for cracks and sweep them to clear away dust, dirt, and waste.
Step 9: Seal the Surface
The best solution to preventing rust is sealing the floors with an appropriate sealant. Concrete sealers protect surfaces from water, oil, staining, de-icing salts, grease, and staining. It’s essential to prepare the concrete before applying a sealant. Here’s how to seal concrete surfaces to avoid future rust stains:
- Strip any existing sealer from the surface
- Use an etching solution to open up the concrete
- Apply a thin layer of sealer using a sprayer
- Leave the first layer of sealer to dry off
- Apply the second layer of sealer in opposite directions to the first
- Allow the sealer to air dry before applying pressure to it
Sealing the surfaces ensures that they’re safe to resist future strains. Since concrete is porous, sealing the surfaces helps prevent grime, dirt, and grease from penetrating the pores and making maintenance easier. Furthermore, the proper sealant prevents rust and contains more staining on the concrete.
Choosing a suitable concrete sealer can be challenging because many options are available. Learning the basics of the many concrete sealer compounds available can help you select the ideal one for your surface.
Whether the concrete is old or fresh will dictate the type of sealer you can use. Some sealers will specifically work for old surfaces and others for new ones. If you successfully removed the rust but have a discolored patch, you may fix it by applying concrete resurfacing or coloring.
Concrete is a sturdy material for indoor and outdoor floors. Unfortunately, it’s prone to rusting, degradation, and damage after some time. At some point, using chemicals to clean the structures is crucial. If your concrete surface has stains, you’ll need to identify the sources of rust, choose the right cleaning solution, gather the necessary tools, and prep the surface.
The easiest way to prevent stains on your concrete is to seal it and fix any noticeable fractures that might permit moisture to penetrate the beam. Now that you know how to remove rust from concrete, consider doing it today to improve your concrete durability. We hope you enjoyed reading our guide on how to remove rust from concrete surfaces.