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Clean Rust Off Concrete

Home Improvement Products, Outdoor Living, Stone and Concrete November 19, 2012 Sonia

By Rob Robillard





This article will help you save time, labor and money by showing you the best way to clean rust off concrete or bluestone. Many homes have concrete and bluestone walkways, steps and patios. The problem is that rust stains can occur from patio furniture, umbrella stands, fire pits or toys. These stains can be very difficult to remove.

Following are the necessary functions needed to easily remove a rust stain from your concrete using muriatic acid.

The metal stand of a patio umbrella created unsightly stains on the patio surface.


Muriatic acid should be a measure of last resort. Use it only after you have already tried less caustic cleaning agents.

Safety Information

As a safety precaution, do-it-yourselfer’s should avoid muriatic acid where possible. Only use muriatic acid after exhausting other cleaning methods like TSP (tri-sodium phosphate), or less caustic concrete stain removers.

In other words, muriatic acid is not the first choice for masonry cleaning but the last resort.

Muriatic acid is a highly reactive liquid acid, and one of the most dangerous chemicals you can buy for home use. It is an industrial-strength solution of hydrogen chloride gas dissolved in water, also known as hydrochloric acid. With the exception of some plastics, muriatic acid can damage most anything it touches, including clothing, metal and skin. It emits a suffocating odor that can quickly burn the lining of the nose, throat and even the lungs.

Typical home applications include heavy-duty masonry cleaning, preparation of masonry for painting or sealing, removal of efflorescence or mineral deposits and pH reduction in swimming pools. If you consider using muriatic acid, please heed all safety recommendations both here and on the product’s label.

Contact with the eyes, for example, can cause irreversible damage and permanent blindness. Contact with the skin can cause severe burns. Dress appropriately; wear safety glasses, acid-resistant gloves, long sleeves and pants, and use a NIOSH-approved respirator equipped with the appropriate acid-grade filter.

Additionally, have a neutralizing agent and a reliable, steady source of water available. Baking soda or garden lime can quickly neutralize the acid if spilled. Water should be freely available in case you accidentally get acid on your skin.

Keep baking soda or lime on hand to neutralize the acid.

Since muriatic acid can damage or kill foliage, cover or wet all nearby foliage with water before application of the acid.

Work in an area with adequate ventilation. Use a fan to bring fresh air to the work area if necessary. Muriatic acid is nonflammable, but the vapors are highly corrosive and irritating. Using muriatic acid indoors is not recommended. The corrosive vapors can begin chemical reactions in metals, leading to long-term permanent damage.


Cleanup & Disposal

In some cases you may need to clean up an accidental spill. Spreading a generous quantity of baking soda or lime (the powdered or crushed type used for lawn or gardens) and adding water will cause a distinctive “fizz” as the chemicals reacts with the acid, releasing carbon dioxide and producing harmless salt and water. Garden lime is less expensive than baking soda and is sold in larger bags.

Muriatic acid should never be poured down a sink or storm drain, or flushed down a toilet. Doing so can cause extreme damage to pipes, dissolve solder and damage the biological balance of your septic system. Throwing away even a closed container of muriatic acid with the trash can be dangerous for trash handlers, their trucks and possibly cause unexpected chemical reactions in landfills. Neutralize your container prior to discarding. (Call your local recycling center for more information.)


How to Use Muriatic Acid

Muriatic acid should be diluted to at least 1 part acid to 10 parts water. For small areas, a quart container of acid is usually sufficient. Mix the acid and water in a plastic container. Always pour acid into water, never water into acid. Mixing the two causes a reaction that gives off heat. This reaction is much more sudden and violent when water is poured into the acid.

Let the acid sit for no more than a few minutes, less if you can see the rust lifting.

Always pour acid into water—never water into acid.