Oxalic Acid

[tanger 14]

Good evening

I have a paver job coming up. The bricks have a lot of irrigation rust on them. After spraying them with ox what is a good dwell time before rinsing.

Would the dwell time be the same for brightning concrete. Thanks Tanger

[Mike Stahmer 14]

Let it dwell till the rust is gone! I would neutralize with something if you are going to seal them!

[Rodney 14]

Mike what would you use to neutralize ox. Water?

[Jonathan Chiplock 14]

Wouldnt citraolic sp? acid work?

[Jeff 232]

I heard Soda Ash will neutralize Oxalic. I dont think I would bother, Id just rinse & rinse again

[Mike Stahmer 14]

Ya, just a very light caustic! Or rinse the hell out of it. The problem is that even after rinsing, the surface will have a acidic PH. Only neutralize if you are going to use a brick sealer. If not, dont worry about it!

[Beth n Rod 1,279]

In a strong enough concentration, oxalic can etch concrete. If you are removing rust be careful with that. Rinsing will help this. Look for foaming or fizzing. If it is acting on the lime, you may see this, usually when the concentrations are high. Sometimes several applications are necessary.

Hope this helps. :)

Beth

[Jim Carroll 14]

if it is a dark color i would neutralize and rinse like crazy, if the oxalic dries on dark colored pavers it will leave a white haze.

[Littlefield 65]

Baking soda dissolved in water will buffer oxalic acid, and leave with a barely over neutral surface. Apply, rinse, repeat. I've been told a tablespoon per gallon will work, I just throw a whole box in a 30 gallon drum.....

[PLD 14]

Rich: Huh?!? You add baking soda to you Ox barrel? That does not buffer anything. The oxalic eats the bicarbonate and reduces your Ox concentration.

[PLD 14]

As for neutralization, I can only say this (again): "Neutralization" is a waste of time and chems unless;

- The next step (after neutralization) likes a Ph opposite of what you have prior to neutralization.

<or>

- The present chem situation will continue to degrade the substrate, and the opposite Ph will not. An example of this is NaOH on wood.

That said, you cannot "neutralize" a chemical unless you know it's molarity and volume present on the substrate. You would then apply the exact volume of chem necessary to convert all the residual chem to an unreactive salt. Without this information (impossible in the field), you will either under apply (Ph remains as is, albeit less volume) or over apply (Ph swings past 7 and opposite reaction occurs.

In the case of wood, the next step is to brighten the wood. Hence, over application of oxalic stops step 1 and prepares for step 2. This is a desirable situation, but it is not "neutralization" as the wood's PH is far closer to 1 (acidic) than it is to 7 (neutral)

That said:

When you seek to stop the action of a chemical ("neutralize"), look on the opposite side of the Ph spectrum. Acids neutralize Caustics and vice-versa. If you need to neutralize oxalic, citralic, or muratic the handiest chemicals to do so are bleach and NaOH. If you need to neutralize bleach, NaOH look for Oxa, Citralic, Vinegar, even lemon juice.

One thing to remember when "neutralizing" is that the purpose is to stop (or mitigate) a reaction that will cause damage if allowed to proceed. Hence, if is often desirable to "neutralize" with a larger volume of a much milder chemical. For example: It makes no sense to neutralize NaOH on your skin with 33% muratic as the cure would be worse than the ailment. Vinegar or diluted oxalic would be a MUCH better choice. However, if I got 33% muratic on my skin, I would not hesitate to neutralize the acid with 12% bleach, followed with copius amounts of water to dilute the bleach.

Anyway, I'm rambling. As a physics student, I was forced to endure alot of chemistry. If you have Q's feel free to ask.

[Jim Carroll 14]

However, if I got 33% muratic on my skin, I would not hesitate to neutralize the acid with 12% bleach, followed with copius amounts of water to dilute the bleach.

Anyway, I'm rambling. As a physics student, I was forced to endure alot of chemistry. If you have Q's feel free to ask.

doolittle while enduring chemistry did you guys ever discuss the reactions of muriatic and 12%. I think I would just stick with the water. I know it can have violent reactions in containers not sure about on skin.

just giving you a hard time:lgwave: