Removing an unsightly stain from your concrete walkway, patio or driveway may be easier than you think. Unsealed concrete is very porous and stains easily. Luckily, you can remove many common stains without the help of a professional. Some stains may even be removed using products that you may already have on hand.
Tougher stains may require a trip to your local hardware store. For the best results, you should always treat stains as soon as possible. You’ll have a much easier time removing a stain if it has not had a chance to set in. The following guide will provide you with information and ideas on how to treat common stains caused by oil, algae, berries, and rust.
Treating oil stains.
Oil and grease stains are very common in driveways and on garage floors. Fresh oil stains caused by cars can often be cleaned up using ordinary dish soap; however, difficult stains may need to be worked on more than once. To treat the stain without buying a special concrete cleaner, you will need liquid dish soap, water, a nylon scrub brush, and an old towel. You should never use a scrub brush with wire bristles to treat a stain on concrete.
The water may cause the wire bristles to rust and the rust can cause a new stain. Wire bristles can also scratch concrete, so for the best results always use a scrub brush with nylon bristles. First, wet the stain and the surrounding area. Next, squirt some dish soap directly onto the stain. You want use enough dish soap to work up a thick lather. Scrub the stain with the nylon brush. You’ll need to put some effort into scrubbing in order to lift the stain.
Once the stain has been scrubbed thoroughly, use an old towel to blot up the excess soap and water. Cat litter can be used in place of the towel if you prefer. Simply spread clean cat litter on the area and let it absorb the excess liquid. Using a hose to rinse the area is not recommended because the oily runoff can seep into the ground and contaminate soil and water. Properly disposing of the towel or litter may involve an inquiry to your community’s waste removal department.
Typically the local law for disposing of motor oil will apply to these items as well. If you prefer to use a commercial product there are a number of them that are specifically designed for lifting oil-based stains. Your neighborhood hardware store is sure to have a good selection of these products available.
If you decide to use a commercial product, speaking with a sales assistant at your hardware store may be helpful. A knowledgeable professional can recommend the best product for your particular problem. Be sure to mention how old the stain is and if the stain has previously been treated with any products.
Treating mildew and algae.
Mildew and algae are quite common and easy to treat. Left untreated mildew and algae will stain your concrete. To treat the problem area, you will need a power washer, hot water, and oxygenated bleach. Chlorine bleach can be used; however, it is toxic and should only be used in small areas where you can control the run-off. Oxygenated bleach, also called sodium percarbonate, is very common and can be found at most hardware stores; it is usually sold as a deck-brightening agent.
When it is mixed with warm water it becomes hydrogen peroxide, which is non-toxic and will not harm nearby plants and trees. Mix 2 parts hot water to one part bleach. Use this mixture in your power washer to spray the problem area. It’s that simple. You should see immediate results. You may want to repeat this treatment periodically to keep the mildew and algae from returning.
Treating berry stains.
Fruit-bearing trees and shrubs can make quite a mess on concrete. Red-colored fruits contain a natural dye that is particularly difficult to remove. Soap should not be used for this type of stain, as it will only cause the stain to set. If grapes, strawberries, cherries, raspberries, or cranberries caused the stain you wish to treat, a solution of hydrogen peroxide and flour may help. You will need flour, hydrogen peroxide, and a nylon scrub brush.
For a relatively small area, mix one cup of flour with just enough hydrogen peroxide to make a thick paste. The paste should be the consistency of peanut butter. Apply the paste mixture to the stain about one-quarter inch thick and cover with plastic wrap. You want to make sure the plastic wrap is securely taped into place because the mixture needs to sit until it is completely dry, approximately 24 to 48 hours. As the mixture dries it will pull the stain from the concrete. This type of stain can be difficult to remove and may require several applications. For larger areas, you may want to purchase a commercial product from your local hardware store.
Treating rust stains.
When treating rust stains never use chlorine bleach. Chlorine bleach will set the stain and make it nearly impossible to remove. The best solution for rust stains is to purchase a commercial product that contains oxalic acid. Oxalic acid is usually sold as a wood-bleaching agent and comes in crystal powder form. You will also need rubber gloves, eye protection, warm water, and a nylon scrub brush.
A long-handled scrub brush would work best for this project to give you some distance from the fumes. It is important that you follow the manufacturer’s safety instructions when using oxalic acid, as it is very toxic and can be absorbed through unprotected skin. Be sure to work in a well-ventilated area and wear rubber gloves and safety goggles. Follow the manufacturer’s mixing instructions; usually, 1 pound of oxalic acid should be mixed with one gallon of warm water.
After preparation, dip your nylon scrub brush into the solution and scour the area. Let this sit for 10 to 15 minutes. Rinse the area clean with plenty of water. According to the EPA oxalic acid biodegrades in about one day; however, keeping kids and pets away from the area for a few days might be a good idea.
After you have successfully cleaned your concrete surface you may want to consider sealing it to help protect it from future stains. To properly seal concrete you need to first etch the surface. Etching products are acid based and eat away a tiny bit of the concrete. This creates a surface that the concrete sealer will adhere to. There are a number of products that are designed for this purpose. Calling in a professional to do this work might be a good idea because the chemicals involved in etching and sealing can be very toxic.
There are many solutions to cleaning stains from concrete surfaces. When in doubt ask a hardware store professional, they will be able to help you solve your particular problem, either by recommending a product or suggesting a home remedy. With a bit of preparation and persistence your concrete surface can be free of stains and well protected.
