How To Clean Concrete Stains
Stains on concrete driveways and walkways are a common problem. Whether it results from automotive fluid leaks, a planter left sitting in the same spot too long, paint splatter or a myriad of other common spills, most stains can be removed or at least mostly removed.
Just like cleaning carpets or fabrics, you should always test the cleaning technique in an inconspicuous place to make certain you will be satisfied with he results. Cleaning should be done when the the weather allows for fast drying. An important thing to note is that cleaning a spot will often lead to a clean spot that stands out just as much as the dirty spot did. When cleaning a spot, plan on cleaning the entire area to avoid a patchy look. Finally, always read and follow the directions on all chemical cleaners and equipment.
We recommend starting with a simple cleaning before advancing to more powerful cleaning techniques. Sometimes a little soap and water with a light scrub is all that is needed.
General, Light-Duty Concrete Cleaning
Use water and a non-metallic stiff bristle brush. Metal bristles can leave behind metal particles which can rust and stain. Scrub in a circular motion to lift out a stain and flush the area with water. If this doesn't remove the stain, try dish soap and water. If dish soap does not work, try powder laundry detergent or scrubbing cleansers like Bon Ami or Comet. Remember, the waste water along with the soap and any other chemicals may damage nearby lawns and gardens. If the water flows out to a gutter, it may not flow to a waste treatment facility as your home's waste water does, there may be laws governing what you can wash into the street. Your local fish and wildlife may be affected by what you wash into the street, and fines can be stiff.
If scrubbing is not adequate, then a low pressure wash is the next step up. Pressure washers can help to pry away difficult stains. Pressure washers must be used which caution. Pressure washers can injure people and animals, can damage wood and pry off loose concrete. Test a pressure washer on an inconspicuous location first. Read more about pressure washers.
Finally, the use of light duty chemical cleaners may be called for. Some of these chemicals may be added to a pressure washer to enhance the cleaning action. Note that some of these chemicals may require you to collect the residue and dispose of them in a manner similar to other household chemicals.
Difficult, Deeply Penetrated Stains
Stains such as soaked in oil, tire marks and ground in dirt may require more aggressive techniques. Chemical degreasers soak in and loosen tough stains. Note that many of these chemicals require that the residue be collected and properly disposed of. Another tough cleaner is muriatic acid and water mix. This acid mixture is tough on stains but it can also weaken the surface of concrete. Muriatic acid requires special handling and may require special ventilation considerations. Use of muriatic acid and other strong chemical cleaners may be best left to professionals.
In extreme cases, sand-blasting or shot-blasting may be required, followed by a top coat resurfacing. These techniques should be left to a professional.
For more information on how to clean specific types of stains from concrete check out our stain cleaning guide.