Your driveway and sidewalks are prime locations for rust stains to buildup. In many cases, if you were to use some form of driveway cleaner or rust cleaner. You would either have to settle for an industrial-grade acid that, more often than not, damages everything on its tracks.
Trying to remove rust stains from concrete can be frustrating especially if they’ve been there for quite a while. Oxalic acid has been proven successful for eliminating most rust spots. There are also some household cleaners such as “ZUD” and “Bar Keepers Friend” that contain oxalic acid.
Here’s how to remove rust stains from cement using oxalic acid:
Mix a pound of oxalic acid bleach with a gallon of water. But before using your homemade rust stain remover, make sure to place tarps or plastic coverings onto the areas near the driveway where water runoffs could occur. Oxalic acid bleach tends to kill the vegetation it comes in contact with.
With the protective coverings in place, dip a mop or large sponge into the bucket and wipe the oxalic acid bleach solution to remove rust stains on cement, whether it’s your driveway or an exterior of your home that needs cleaning.
Allow the solution to remain on the rust stains for two to three hours. This will provide more than enough time for the oxalic acid to remove rust stains from the cement. Then brush the affected areas with a stiff bristled brush or broom. Then rinse the treated area with a garden hose.
If there are still rust stains remaining, apply the oxalic acid bleach solution a second time onto the affected areas.
Finally, wet the concrete driveway with the garden hose and drop two to three drops of dish detergent onto the affected areas. Scrub the areas you’re treating with a broom, then rinse soap away with the garden hose.
But what if the oxalic acid doesn’t work? What are your options?
Then you can try using trisodium phosphate or TSP. This is a powder that can be found at most home improvement stores and paint stores. Mix half a cup of TSP with half a gallon of hot water, pour it over the stain and let it sit 15-20 minutes. Then scrub with a stiff bristled brush and rinse with water. Repeat the procedure a few times if necessary.
But if your attempts to remove rust stains from cement doesn’t bear fruit, then you can use an etching solution by mixing four (4) parts water to one (1) part muriatic acid as a last resort. Bear in mind that this method actually eats away the cement surface material. So you’re not actually cleaning the concrete, but removing the cement that the rust stain has bonded with.
Of course, this is just a last resort. When you remove some of the cement, the surface is weakened and becomes more susceptible to chipping and scaling. You can correct the situation by putting a coat of clear concrete sealer on the surface of the driveway.
It is highly recommended to exercise extreme caution with products that contain acid. Wear rubber gloves and safety goggles and keep clean water nearby in case of accidental splashes.