How to remove battery-acid stains from a concrete floor

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Q: How can I remove a battery-acid stain from a concrete garage floor? It was caused by a golf cart.

A: Because acids attack concrete, the affected area may be darker and altered in texture, and that limits your options, said Terry Collins, concrete construction engineer with Portland Cement Association.

One approach is to treat the whole floor with an acid wash to stabilize the color and texture. Basically you’ll be removing a small amount of the surface so it all looks the same. Typically, this is done with muriatic acid, and it might be best to hire a contractor. If you feel confident about doing it yourself, be sure to wear gloves, eye protection, long sleeves and pants.

If you can live with the texture change and just want to remove the dark color, Collins suggests that you try treating the area with household chlorine bleach. Some people have successfully treated dark spots on concrete with diammonium citrate.

Free publications on removing stains from concrete can be downloaded from www.cement.org (click on “bookstore” and search for PL861 and PL961).

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