How to Clean Stains from Concrete

Does your front walk or driveway look like a Jackson Pollock painting? Read on for some methods for getting rid of unsightly stains and blotches in concrete and masonry surfaces.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Hose and nozzle
• 3-to-5 gallon bucket
• Clay litter
• Degreaser or commercial driveway cleaner
• Laundry bleach
• Oxalic acid product or granules
• Push broom or straw broom
• Eye protection and protective gloves
• Pressure washer, if available

1. Treat oily stains first. For fresh oily stains, start with clay litter (generic—the cheap stuff, because they all work the same). Cover the stained areas with clay litter and let sit for a half hour or more to let the clay soak up surface oil. For older, dry oil stains, skip the clay litter part. Next, use a good quality degreaser or driveway cleaner to attack the deeper oily stain, letting it soak in for about 15 minutes. Finally, hose off and brush with a push broom or straw broom, or wash residue off with a power washer.

2. Attack rust stains with oxalic acid wash. There are commercial rust removers that contain oxalic acid, or you can get the granular form at the hardware store. Apply the mixture as directed and let it soak in for 15 minutes to an hour; then flush with a hose or pressure-washer.

3. Treat mold and mildew stained areas with a bleach solution, or with a pressure washer. Add a quart of laundry bleach to a gallon of cold water and pour over dark areas of mildew stains. Wear latex gloves and eye protection when cleaning with bleach solutions. Rinse the treated area thoroughly with a hose or pressure washer.

4. Finish off any stubborn stains with a solution of muriatic acid (hydrochloric acid). Buy a gallon jug at the hardware store and use very carefully. It’s a strong acid. Fill a bucket with a gallon of cold water and slowly add about a quart of muriatic acid. Wear rubber gloves and eye protection, and avoid breathing any fumes coming off the bucket. Make sure your hose is ready for rinsing, then carefully pour the acid solution on stained areas. The muriatic will be strong enough to remove most types of stains, and dissolve some of the lime in the cement; so let it work for a few seconds and start rinsing thoroughly. Avoid brushing, which may spread the acid around where you don’t want it. Hose down until there are no residues left.

Tips & Warnings

• If you have access to a pressure washer, use it as a final wash after you have treated individual stains as outlined above.
• Never add water to acid because of the danger of fumes, heat or splashing liquids. To dilute an acid, always pour the acid carefully into water.
• Always wear protective clothing, gloves and eye protection when handling acids, alkalis or solvents.

[chava812]

on 8/23/2008 Good article - will this remove stains from dirt/clay that has discolored concrete as well?