Disclaimer:
Safety is the first concern when working with muriatic acid. Please carefully read
all of the safety section before attempting to acid wash anything.
Acid Wash - Safety Frequently Asked Questions
Acid Wash - General Frequently Asked Questions
Acid Wash - Safety - Frequently Asked
Questions
What safety equipment do I need
before I can safely start working with acid ?
Safety glasses Rubber gloves Rubber boots Hose with a squeeze type of nozzle to quickly wash any
part of the body that might come in contact with the acid Respirator if you are working in an enclosed area. While working with acid, what safety
concerns should I have?
ALWAYS WARE YOUR SAFETY GLASSES Always add the acid to the water and not water to acid, a
reaction may occur. (more in-depth explanation) Chose one location for mixing acid with water where
the hose is accessible. Always have a hose within an arms reach when
mixing. Use rubber gloves instead of cloth gloves so the acid
won't absorb into the glove and on to the skin. Always reseal the unused portion of the acid container
while you are on the slab working. A respirator will be necessary if you are working in
an enclosed area Be careful of the fumes that can occur while mixing
and while applying the acid solution. If you breath one of these acid
clouds it can be very painful. When I clean up what safety concerns should I have?
Try to use up all the acid that you've mixed. If you
don't use all the mixed acid, you can save it in a separate container, or dilute any unused
acid as much as possible (100-1) then pour in out on a gravel area. Wash everything thoroughly Yes, it can burn your skin, but if it's rinsed off quickly
it will not burn. If you get acid on any cuts or scraps that have not healed
completely, this will sting, so rinse it off quickly. For these reasons, ALWAYS keep a hose handy. Always where your safety glasses. Can I neutralize the acid without
adding water?
Yes, lime with work to neutralize the acid. If you spilled acid in a location where the run off
from a hose would harm plant or animal, add lime to neutralize the
acid. Where can I find a MSDS Material Safety Data Sheet to read?
Here is a link to a MSDS for Muriatic acid. What can I use to clean up Muriatic Acid?
Steps to take if material leaks or spills:
Using recommended protective equipment, carefully add lime or sodium carbonate to neutralize acid. If large spill, first dike to contain. Pick up and put residue into container for disposal. Flush area with water. Collect for disposal or sewer.
http://www.aldenleeds.com/html/muriatic.html
Why is acid always added to water, and not the reverse?
Acid Wash - General - Frequently Asked Questions
What do I need to get started?
All your safety equipment mentioned in the safety section of this document. Be sure to read it carefully
A garden hose long enough to reach all of the concrete you are washing.
Nozzle for the hose type mentioned in the safety section.
Muriatic acid- approximately one gallon for every 300 square feet of concrete
A clear plastic spray can used to apply the acid/water solution.
A street broom, one with stiff bristles.
A dry day, the concrete MUST BE COMPLETELY DRY.
Why do concrete finisher acid wash concrete?
Acid etches or eats away any white milky stains that are left on the newly exposed aggregate concrete
Also the color of the concrete surface should darken and be consistent.
What does the acid do to the concrete?
Muriatic acid reacts with cement and lime in the concrete by . It cleans up the aggregate in an exposed aggregate finish so that a sealer can be applied to a clean surface.
What type of concrete finish would I acid wash?
Exposed aggregate that was recently poured and not been sealed is the type of concrete surface that is most commonly acid washed.
Older concrete, 6 months or more should be pressure washed first to remove moss and grim that the acid can't remove.
I never acid wash concrete with a broom finish, like city side walk.. Acid will harm the broom finished concrete.
How do I prepare the acid for use on my concrete?
Always add the acid to the water, and not the reverse (Please read this explanation why).
The most important thing is that your acid to water ratio is consistently kept throughout the job. I start with a ratio of 1:4 One part acid and four parts water. I use a 2 or 3 gallon plastic spay can I can see though for easy mixing.
Chose a location for mixing the acid solution off the work surface. This way you will nor spill acid or water on the dry concrete.
What type of acid is used to wash concrete?
Muriatic acid, it can be bought at most any home improvement store. It is sold in one gallon plastic jugs. I buy one gallon of acid for every 300 sq. ft. It depends on how strong you mix the washing solution.
I poured a new driveway should I acid wash it?
If the your driveway is exposed aggregate and no sealer had been applied.
Will the acid harm my grass and plants?
Yes, grass and plants that come in contact with the acid/water solution can be harmed, but usually only grass that is within 2-3 inches of the concrete edge will turn brown. Soak the grass and plants around the work area. The more the acid is diluted the better.
Wash everything thoroughly
How do I prepare the concrete surface for the acid wash?
The concrete surface MUST be dry.
Try to do it on a clear day where the surface will dry. If you are going seal the surface you can seal it as soon as it dries.
Will the acid harm existing concrete, like my sidewalk?
Yes, broom finish concrete that has not been sealed will be discolored
The day before I acid wash, I will apply sealer any concrete that is in the path of the run off from the acid wash.
How large of an area should I work at a time?
Don't work an area larger than can be easily rinsed off before the acid solution dries.
On a cold day you will be able to put more acid down before rinsing it off, but one a hot day you may only be able to work 100 sq. ft.
Don't let the acid dry out before rinsing with water. This can discolor or yellow the concrete.
Does it matter where I start washing?
Yes, on larger jobs start at the lowest part of the work area. This will allow you work an area small enough so the acid does not dry on the surface
You do not want the acid to dry on the concrete surface. This can discolor or yellow the concrete.
When rinsing be careful not to get water on the dry concrete the has not been washed. This will dilute the acid before it can work.
When I put acid on the concrete it foams, should this happen?
Yes, you can tell it working when it forms. Ideally I will apply the acid solution until the foaming stops.
Remember it is important to keep the ratio of acid to water consistent, and that the concrete is dry.
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