Review / How To Muriatic Acid to Brighten Concrete

swanicyouth

swanicyouth

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I've been wanting to "deep clean" my garage floor for a while. I know nothing about concrete. I mentioned it on here and went to Home Depot, and it seemed like the best stuff out there is muriatic acid. So, I decided to learn a little but about it before using it.

First off, this stuff is a dangerous acid. I usually don't worry about gloves, safety glasses, and respirators with stuff like Iron X or Meg's Chrome Wheel Cleaner because I use it so infrequently and I'm just careful. This stuff scared the crap out of me, so I used gloves and safety glasses. If hydrochloric acid splashed in your eyes it can make you blind - permanently. If it gets on skin it will eat it away.

Muriatic acid is just another way of saying hydrochloric acid. Its a highly corrosive strong mineral acid. Interestingly enough, its used in (part of) the process to regenerate the resin for DI water systems, like the resin used in the CR Spotless. The hydrogen ion is used to remove the calcium and sodium that the cation exchange part of the resin (mixed bed) takes out of the water. this is done so the resin can be used again.

It apparently can be used to "etch" concrete or to clean and brighten it depending on dilution. The cleaning dilution is 12 oz a gallon, so that is what I used. When mixing this stuff, you always add water to acid, so if there is any splash back its likely to be just water.

When I was mixing it, a little bit got on the glove. I knew this because even through thick gloves I could feel it warming up. Even after it was diluted, when being applied to the concrete it started to smoke.

The method I used to apply it was to "broom it on" with a nylon bristle shop broom and scrub it into the concrete. Right away you could see the dirt coming out of the concrete. This was dirt that didn't respond to stuff like Simple Green and surfactant based floor cleaners. The floor was already pressure washed with a "turbo" tip.

Interestingly enough, at this concentration it didn't remove stains. While the overall effect is a brighter, whiter, cleaner concrete - most of the stains are still there. I'm guessing a stronger dilution may help, I may try that in the future. What it did do is just improve the overall look of the floor, which pretty much was what I was going after. But, I was disappointed it did little to the stains, which gives the floor an overall "dirty" look.

Here is some before and after pics. Note the black stain as a reference point. It wasn't removed. Also, note the 50/50 area in the after pic where I stopped applying the product. The area behind (dirty area) is how the floor looked before

Before:

a4eru9yv.jpg


After:

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You can see in the after pic if you compare the frontal area how the concrete was brightened quite a bit, but the stain remains.

Another "50/50" showing just how bad the floor was:

bu7ady2a.jpg


Here is an after pic of the whole floor. Overall, kind of underwhelming due to the stains remaining. I may try it again at higher concentrations:

upe3y3am.jpg


If anyone uses this stuff, be careful!
 
Those stains have leached into the concrete fairly deep, it seems.

In order to remove those stains...
(without having a stronger solution of the muriatic acid take off/etch a layer of your garage floor):

Get some tri-sodium phosphate (TSP), in powdered form,
and use it to scrub the stain.

Sprinkle the TSP over the stain, add enough water to make a paste,
and scrub the stain with a good nylon brush.

Repeat if necessary.

Of course proper PPE is a must.

-"Final-wash" with a household detergent...
Even Dawn will work!! :eek:

Bob
 
I wonder if TSP would eat up the concrete paint I have on my floor at the shop. I try to keep it clean but I can't control some cars that come in with leaks getting repairs.
 
Muriatic acid is what we add to swimming pools to lower the pH. I always have a few gallons on hand, and have to add it almost every week because of the water in Phoenix. It's not so dangerous when you're adding a quart or two to 27,000 gallons of water.

By itself, it will brighten concrete, but it won't take out the stains.

There's lots of DIY advice on the Internet, and most of them don't work all that well.

As Bob said, TSP will help. But, you need to leave the paste on the concrete. You're trying to draw the stain out of the concrete, not washing it off the surface. Concrete is porous, and oil, grease, etc. get into the concrete.

For a fresh oil spill, nothing works better than kitty litter.

BTW, don't forget to do a "test spot" first :xyxthumbs:

Jim
 
Anthony@zerboautoworks said:
I wonder if TSP would eat up the concrete paint I have on my floor at the shop. I try to keep it clean but I can't control some cars that come in with leaks getting repairs.
Click to expand...

My customers with auto repair shops, machine shops etc. use a device they call a Zamboni. The floors are generally sealed with epoxy, not paint.

Search for Zamboni floor cleaners, and you'll find all manner of machines big and small to keep your floor looking good.

If you just search for Zamboni, you'll get ice rink resurfacing equipment (those big machines that come out at hockey games)

The TSP may or may not remove the paint. Do a test spot!

Jim
 
Well not everybody has a perfect sealed shop floor with epoxy, my floor was extremely trashed with caked on oil grease,etc from 30 years of use and it seemed they never cleaned it, I hit it with degreaser and went to town with a high psi pressure washer and the oil/grease was flying off in chunks I would have spent way to much time and money getting that floor prepped for epoxy on 50x60 building, that is why I painted it with concrete paint.
 
Maybe I could use Muratic Acid to dissolve the Stalagtites on my trucK.:doh:

With the hard water here, and how long I've been living here in NM, I'm surprised my truck isn't bonded to the carport slab.
 
Thanks for all the advice. I'll try the TSP. I actually had it in my hand and the guy at Home Depot said, "that stuff is OK, but use this".
 
I don't know if this would help but I've used this in the past for metal etching on homemade guitar effects pedals. (circuit boards, enclosures, etc). I've done a 1:1 mix with hydrogen peroxide for those. Might want to try that on a test spot.
 
Ah, the wonder of communications on the Internet. :xyxthumbs:

Wasn't picking on you Anthony, just thought I should include the comment about epoxy because that's what's on the floors where I've seen people using the Zambonis. If you research this kind of cleaning device, make sure that what you get is designed for the kind of floor surface you have.

It's obvious from the photos that you did a lot of hard work to clean up that floor.

Best regards,
Jim
 
Nice write up. That stuff can be potent like you said. I have a nice clean spot in the driveway from HCl I used in a battery. I may use it on my porch this summer to brighten it up.

I think you have the mixing order for acid and water backwards. The rule is always add acid to water.
 
MarkD51 said:
Maybe I could use Muratic Acid to dissolve the Stalagtites on my trucK.:doh:

With the hard water here, and how long I've been living here in NM, I'm surprised my truck isn't bonded to the carport slab.
Click to expand...

If you paint your truck lime green, it might grow more :poke:

When I moved here to Phoenix, everyone told me how hard the water was (especially the water softener sales people).

It is hard, but I grew up next to Lake Michigan. That water was so hard, that if you dropped it, it would break!

Never bought into the water softener concept. I am trying to figure out what to do to slow up the water spotting when I wash the cars. At this time of the year, it's so dry that water evaporates while you move from one side of a car to the other.

Now that my wife is being a fanatic about her restored old Pathfinder, she points the few waterspots out to me every time. But, she hasn't helped to get it dried quicker.

Jim
 
Hydrochloric acid (or any acid for that matter) will not be acting to clean the concrete, it will be dissolving it. Think back to your chemistry at school, concrete uses cement which is lime based which is alkaline. Acid of course reacts with alkaline materials. So when someone is using acid on concrete, they are dissolving the top layer and leaves behind some underlying layer which has not been exposed to soiling.

Unfortunately, acids are really not very good with grease, oils, hydrocarbons. They can remove them but, inspite of the dangers of the acids, they are rarely effective. This is where an alkaline product like TSP comes on - this will be vastly better at removing oily stains and residues. Even then, things like paint are going to cause problems. The cleaner is unlikely to remove some paints and the brightener (acid) wont penetrate them so wont be able to dissolve the underlying concrete and effect the removal.

For concrete removal and brightening purposes, hydrochloric acid is basically the cheapest thing out there. Unfortunately you need to proceed with care, not only because of the health and safety, but because it is not cleaning, it is dissolving. This is a destructive process and you leave concrete compromised. The very simplest consideration is that you will lead to pores being opened out and this is where soiling will go in the future - the next time you do the job, you may well have a much tougher time. So really you should try to seal the surface after treating it in this way.

As for health and safety, believe it or not, hydrochloric acid is less dangerous than many automotive cleaners. One that immediately jumps to mind is Megs wheel brightener - HCl could blind you but this fluoride based wheel cleaner is toxic and it could potentially kill you. Non-acid wheel cleaners are often more dangerous than HCl. One of the most popular trade products here in the UK (which has now become a detailing product, somehow) is actually a level worse than HCl products. HCl is classified as corrosive and causes burns, this wheel cleaner is corrosive and causes severe burns (this is actual regulatory terminology). Yet, inspite of this, users often appear on the major UK detailing forum asking how to use it, having never read the label. This product would blind you within seconds if you got it in your eye (notably worse than muriatic acid) yet users often don't even have safety goggles, much less the recommended eye bath in case of accident. Certainly within the UK, detailers have no idea about the dangers they are in and any attempt to highlight these dangers can be met with total hostility and are ultimately ignored.
 
Mr Megane said:
Hydrochloric acid (or any acid for that matter) will not be acting to clean the concrete, it will be dissolving it. Think back to your chemistry at school, concrete uses cement which is lime based which is alkaline. Acid of course reacts with alkaline materials. So when someone is using acid on concrete, they are dissolving the top layer and leaves behind some underlying layer which has not been exposed to soiling.

Unfortunately, acids are really not very good with grease, oils, hydrocarbons. They can remove them but, inspite of the dangers of the acids, they are rarely effective. This is where an alkaline product like TSP comes on - this will be vastly better at removing oily stains and residues. Even then, things like paint are going to cause problems. The cleaner is unlikely to remove some paints and the brightener (acid) wont penetrate them so wont be able to dissolve the underlying concrete and effect the removal.

For concrete removal and brightening purposes, hydrochloric acid is basically the cheapest thing out there. Unfortunately you need to proceed with care, not only because of the health and safety, but because it is not cleaning, it is dissolving. This is a destructive process and you leave concrete compromised. The very simplest consideration is that you will lead to pores being opened out and this is where soiling will go in the future - the next time you do the job, you may well have a much tougher time. So really you should try to seal the surface after treating it in this way.

As for health and safety, believe it or not, hydrochloric acid is less dangerous than many automotive cleaners. One that immediately jumps to mind is Megs wheel brightener - HCl could blind you but this fluoride based wheel cleaner is toxic and it could potentially kill you. Non-acid wheel cleaners are often more dangerous than HCl. One of the most popular trade products here in the UK (which has now become a detailing product, somehow) is actually a level worse than HCl products. HCl is classified as corrosive and causes burns, this wheel cleaner is corrosive and causes severe burns (this is actual regulatory terminology). Yet, inspite of this, users often appear on the major UK detailing forum asking how to use it, having never read the label. This product would blind you within seconds if you got it in your eye (notably worse than muriatic acid) yet users often don't even have safety goggles, much less the recommended eye bath in case of accident. Certainly within the UK, detailers have no idea about the dangers they are in and any attempt to highlight these dangers can be met with total hostility and are ultimately ignored.
Click to expand...

Mr Mengane isn't the only one with a chemistry background here. The danger of HCl depends on the molarity of the product you are using. We all actually have HCl in our stomachs to help dissolve food. The molarity is the total amount of hydrogen and chloride ions per volume. I don't know what number is for this product.


But I felt this stuff burning through a glove and watched it eat concrete. I wouldn't say "non acid wheel cleaners" (surfactant based) or more dangerous than this stuff. Its not dangerous in the sense its carcinogenic (obviously not if its in your stomach), but it definitely can burn you skin and blind you (permanently) if it gets on the appropriate areas of your body.

To me, that's pretty dangerous.

I'll give the TSP a try.
 
swanicyouth said:
I wouldn't say "non acid wheel cleaners" (surfactant based) or more dangerous than this stuff. Its not dangerous in the sense its carcinogenic (obviously not if its in your stomach), but it definitely can burn you skin and blind you (permanently) if it gets on the appropriate areas of your body.
Click to expand...

It isn't a case of what you think, nor what I think - there are regulated hazard classifications which have been used and agreed for years if not decades. I am not saying all non-acid wheel cleaners, just some.

Let me give you the regulations:

Hydrochloric acid -
10-25% - Irritating to eyes, skin and respiratory system
>25% - Causes burns

Note here that hydrochloric acid exists at a maximum of 36.5% w/w (you simply cannot dissolve more hydrogen chloride than this in water). That means that to warrant the 'Corrosive - causes burns' means you need to use not 25% of that hydrochloric acid you buy, you need nearly 70% of the HCl you can buy before it is considered corrosive. So if you were to dilute it by half, your result would be an irritant. If you were to dilute it 1 part to 3 parts water, it would not even warrant classification. Again, these are the regulations, they are based on years of measurement and data.

Now, look at sodium hydroxide, the most potent of the alkaline ingredients (not a necessary ingredient, but a cheap one which is found in everything from APCs to oven cleaners). Keep in mind we are talking about the ingredients in isolation - NaOH often exists in formulations but is neutralised by acidic components so thus becomes harmless salt - in a non-acid wheel cleaner, no such compensation exists. Now this is commercially supplied as pearls or flakes at 100% level. The regulations:

Sodium hydroxide-
0.5-2% - Irritating to eyes and skin
2-5% - Corrosive, causes burns
>5% - Corrosive, causes severe burns

That means that 0.5% sodium hydroxide solution is equivalent in hazard to hydrochloric acid diluted to approx 30% as supplied. Moreover, no matter how concentrated HCl is, it never considered sufficiently corrosive to warrant the severe burns classification.

The point here is that inspite of first impressions, you will find that there are numerous automotive care products which are much more dangerous than hydrochloric acid. With the likes of the wheel cleaner I refer to, the user should use full protective gear like you have done for HCl but this is almost never the case.
 
I thin we are talking about two different things. "Non-acid" wheel cleaners to me means surfactant based type products. "Non acid" wheel cleaners to you means strong alkaline wheel cleaners, which probably shouldn't be messed with either unless no alternatives exist.
 
swanicyouth said:
I thin we are talking about two different things. "Non-acid" wheel cleaners to me means surfactant based type products. "Non acid" wheel cleaners to you means strong alkaline wheel cleaners, which probably shouldn't be messed with either unless no alternatives exist.
Click to expand...

I wasn't meaning to take specific example, rather the message was to take very careful note of the hazards associated with the products you are using. You have shown a responsible level of caution whilst working with a strong acid and I wish others would stop automatically assuming that a car care product is going to be so much less dangerous than a generic acid.

You might be surprised what is in your non-acid cleaners, perhaps it is different in the US but in the UK and europe, non-acid will routinely mean pH in excess of 13.
 
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