Concrete floors and driveways can become stained with a variety of substances ranging from oil and other automotive lubricants, paint, wood stains, and even from the rust residue of metal objects that come into contact with the concrete. Sealants provide some protection, but stains will occur; and the ones originating from the causes mentioned here, tend to be profound and lingering. Household soaps and solvents may remove smaller and fresher stains, but larger and older stains will often require a stronger solution to achieve removal. In these circumstances muriatic acid may be employed to remove the stains.

Please note, muriatic acid is basically hydrogen chloride mixed in water. The type sold in hardware stores is 31.45% acid to 68.55% inert ingredients. It is a heavily corrosive liquid acid which can cause severe burns to the skin and eyes; it is in fact one of the most hazardous materials that can be purchased for domestic use. Make certain to follow all safety instructions and employ all of the precautions related to the transportation, handling, use and storage of the muriatic acid that are mentioned on this page and those that are posted on the muriatic acid container itself.http://www.osha.gov/SLTC/healthguidelines/hydrogenchloride/recognition.html<ref>

Read on, and you will learn how to clean concrete driveways with muriatic acid, safely and effectively.

Before using muriatic acid you must prepare yourself, and the area to be treated, to use it safely. Always use extreme caution as muriatic acid is very corrosive and can cause severe damage and injury when used improperly. The golden rule is to never let it come in contact with your skin or eyes, as severe burns can occur.

'Safety Attire Make certain to wear a NIOSH-approved respirator with the appropriate acid-grade filter. These are readily available at any hardware store where muriatic acid is sold. Also, wear rubber boots, rubber gloves and vinyl coated overalls rated to be acid resistant. Eye protection should also be worn at all times.http://www.cdc.gov/niosh/pdfs/87-108.pdf

Please note that these items will provide you with nominal protection from accidental casual contact, but extreme care should always be taken.

Acid Neutralization Make certain to have a steady water source nearby, such as a garden hose. This is to be used to immediately rinse off any acid, no matter how small the amount, that may have come into contact with your skin.

Also, have baking soda or garden lime nearby to place on any acid that may have spilled. This will neutralize the acidity.http://www.newton.dep.anl.gov/askasci/chem03/chem03286.htm http://www.naturalhandyman.com/iip/infxtra/infmur.html

Ventilation If using the muriatic acid on concrete floors that are indoors, make certain that there is sufficient ventilation and circulation of fresh air. The vapors released from muriatic acid can be corrosive and irritating by themselves.http://www.all-things-concrete.com/acid-cleaning.html

Even though the muriatic acid sold for domestic and household use is only 31.45% pure, it must still be diluted in water prior to being used. The concentration of the solution should be one part muriatic acid to twenty parts water. If the solution is to be used outdoors, and the stains are particularly intense, the solution could be strengthened by using one part acid to ten parts water. Never use the muriatic acid directly.http://www.ocsresponds.com/ref/msds/msds-hcl.pdf

Remember, that as with any acid, the acid should always be added to the water and never vice versa. Adding water to acid can cause a violent reaction that could splatter you with acid.

The acid solution should be prepared in a plastic bucket, never a metal bucket. Measure the water to be used and place it in the bucket and then add the corresponding amount of acid into the water in the bucket.

Identify the location of the stain that you will be treating with the muriatic acid solution. Giving yourself an 18 to 24 inch margin from the border of the stain, apply an outline with a 1 1/2 to 2 inch wide band of garden lime or baking soda to catch and neutralize any muritaic acid that may overflow.

Apply the diluted muriatic acid and water solution with a scrub brush directly over the stained area. Saturate the stain area but minimize overruns.

Allow the solution to rest on the stain for 15-20 minutes, then scrub with the brush. You may repeat the process once more if the stain did not remove completely.

Neutralization of Work Area and Tools When finished, apply garden lime or baking soda liberally over the acid soaked area. This will neutralize the acid so that you may rinse it off as a harmless salt.http://www.elmhurst.edu/~chm/vchembook/183neutral.html<ref>

If any muriatic acid water solution is left unused in the bucket, you may neutralize it by placing 4 cups of garden lime or baking soda into another 5 gallon plastic bucket, and then slowly and carefully pour the remaining acid-water solution into it, stirring with a wooden paint stirrer to neutralize it.