Brighten Concrete

[troyt 14]

I have a job brightening concrete, I used oxalic acid and did an ok job, but the owner had a chemical she borrowed from her brother "dairy farmer" that she spilled a little on the concrete, and turned it white, like freshly poured concrete. I failed to ask what it was, any ideas what it could be that she spilled, and no it is not paint, lol. I think she said it was an acid.

[charlie 14]

Probably muriatic acid.

[CCPC 26]

I'm not sure about the answer to your question, but if you don't mind I thought I might hijack your thread for a few related questions.

I have never brightened concrete with oxalic or any other acid for that matter so I was hoping someone could answer a few questions for me afte helping Troyt.

1) I read on another post to mix 2lbs of Oxalic for a 5 gallon pail, does this sound wright? Also, should I mix with cold water or hot water?

2) I could not find a straight answer on how long to let it dwell. How long should I let it dwell before rinsing or should I not rinse?

3) What kind of pump up sprayer would be a good choice for this task?

4)A lot of times after cleaning a driveway, I spray chlorine on it and leave it there. Obviously this would not work if I wanted to use Oxalic as well, so should I use oxalic first, rinse well, then apply the chlorine, or should I apply the chlorine first, rinse, then apply the Oxalic?

answers to these questions would be greatly appreciated:)

Lance

[troyt 14]

Is muratic hard on the life of the concrete, I have read that even short dwell times can cause the concrete to degrade faster.

[One Tough Pressure 580]

Yes, Muriatic is hard on the concrete and can shorten the life span considerably.

[John Orr 206]

The "farmer's" solution may have been a stronger mix of oxalic. Try it, it will brighten faster and whiter.

Lance,

1) I use approx 8oz/gal - a little stronger if needed. The hotter the water, the easier it will mix. It does not have to be hot, just warm.

2) As far as dwell time, I leave it on until the rust is gone (vinyl) and leave it on, without (usually) rinsing, on concrete.

3) I use a backpack sprayer from HD. It holds-up very well. I also one for spraying chlorine as well as SH.

4) I do the chlorine first.

Hope this helps.

[PressurePros 249]

I have mixed oxallic so concentrated it crystallizes as soon as the water cools down and it has never turned concrete white before my eyes. IMO, that was muriatic acid

[Paul B. 523]

Muriatic acid tends to darken concrete, and is mostly harmful if not diluted properly. When highly diluted, such as in Prosoco's Vana Trol (diluted 1:4 or more), it does a great job of cleaning without causing damage.

Rust removers that contain phosphoric acid, such as Zep's "Lime, Rust, and Calcium Remover" or Prosoco's "Ferrous Stain Remover" tend to lighten concrete.

CCPC,

When spraying acids, chose a pump up sprayer with Viton seals, as they are compatible with acids. I prefer the Chapin 3 gallon #2279 (or equiv.) with safety relief valve. I modify them by replacing the stock hose with longer, clear braided hose.

[CCPC 26]

Paul and John, thank you very much for the help.

[troyt 14]

I bought some muratic acid, and poured in on a piece of concrete at home and it turned yellow, mind you that was at full strength.

I went down to see if I could find out what she had, and she brough it out in a glass marshmellow fluff container that her bother had given here. Here was the situation, the glass container was in a plastic bag, and she walks out swinging the bag from side to side. She did not know what was in it, but she poured some on some aluminum around her windows and it cleaned that real nice, but some spilled onto the concrete and whitened it up real nicely.

She called her brother, and I spoke with him on the phone, he told me where he picked up at in a five gal container, but did not know the active ingredient. It was called Nu Bright.

I went down to the trailer sales department, and they pulled a container, because they did not know what was in it. Sulfiric acid and Hydrofloric acid, it was supposed to be diluted 1 to 40.

I called the lady back, and told her I wouldn't be swinging that around like that if I was her, and gave he the information and stories that I have read about Hydrofloric acid, bad stuff.

Anything work like Hydrofloric Acid, but not so dangerous?

[EmpirePW 14]

Anything work like Hydrofloric Acid, but not so dangerous?

Ummmm... Diluted Hydrofloric Acid maybe?

[RyanH 14]

The solution contains hydrofluoric and sulfuric as a matter of manufacturing processes, not because the sulfuric does anything special. HF acid is EXTREMELY dangerous and should not be used unless very careful precautions are taken. As an acid, HF is particularly weak, but its effects on the body are very hazardous. Tell that lady to quit treating it like apple sauce and treat it with the respect it deserves.

A good substitution would be something that is used to get rid of salts and oxidation. Salt Away, Salt-X, and other similar products should work. Marine supply stores may carry this stuff, but you can get it online if you can't find it locally. The good thing about HF is that the fluoride ions bond so well with the cations in the oxidations (cations are things like sodium, calcium, iron, etc. ions...they are formed when the metals and their salts dissolve in water...the fluoride ion will bond with the cations and allow you to wash them away) and allow you to thoroughly clean an oxidized surface (like aluminum oxide or aluminum chloride) which explains why it worked so well on the aluminum surfaces. HF is also used to etch glass, so I wouldn't be using it around windows. Also makes me wonder how brittle that glass jar had to be. And even diluted HF can be dangerous. The amount of "raw" HF required to do a job is the same...if you dilute it you just use that much more solution to get the final results.

Muriatic acid is hydrochloric acid and is rather strong. Many suggest using phosphoric acid as a substitute. The grout cleaner i use contains a diluted solution of sulfuric acid and works rather well at lightening the grout in areas where normal traffic and mopping has darkened it. Since grout/concrete is porous, many stains are set in and can not be removed chemically without degrading the concrete itself...just let your customers know about this.