Got a project I am starting this week. It is a wall with brick on the top half and limestone on the bottom half. Original contractor after construction was to seal it and did a pretty crappy job. The brick is showing efflorescence and the limestone has mold/algae growth.
I was going to acid wash the brick to remove the efflo and then clean the limestone.
My question is - I will spray the acid on the brick, scrub and dwell. Before rinsing I was thinking I could spray SH on the brick to neutralize the acid before rinsing so avoid having active acid come in contact with the limestone. I also though it might help reduce toxicity to the grass. The alternative I came up with is to tape and plastic sheet the limestone (their is a decorative precast molding between the top brick and bottom limestone). This would protect the limestone but run-off would go in the grass (Customer is fully away of potential grass burning between the acid wash, SH wash and solvent sealer application).
Maybe @CaCO3Girl can chime in if my thought is valid or process is going to work?
The acid used to clean the Eff off of brick is usually hydrochloric in some way. it’s the HCl that causes the toxic chlorine gas.
As for the other acids you mentioned, they are weak, as in Oxalic is barely regulated as a corrosive and citric isn’t regulated at all; it does so little damage they didn’t see a need.
You NEVER want to add a strong acid to a STRONG base…that’s where problems occur because they fight for dominance. Acid has a pH below 2, SH and caustics have a pH above 12.5, water hangs out between 6-8. The reaction of a pH 1 and a pH 13 can involve gasses being released, the water heating up to scalding levels, noxious fumes, and all around dangerous conditions.
I don’t think anyone on here advocates to rinse with oxalic, then dump SH right on it…it’s more like oxalic, rinse with water, rinse with water, rinse with water, then add the SH.
I have always used baking soda to neutralize acid while doing flat work.
I would imagine if the brick work was layered you could put the baking soda before the surface change to neutralize the acid, just a thought, probably wrong.
It’s an interesting theory, but in the end I think it is flawed. The pH reaction isn’t instantaneous, and depending on how much acid there is you could have a chemical reaction strong enough to harm the surface.
I also tell people to use baking soda to neutralize acid and caustics.
The wall is over 1400 ft long. Brick on top and limestone on bottom.
Initially, I was planning to use tape and plastic to cover the limestone block as muriatic acid being used to remove the efflo on the brick will eat away at the limestone block. Maybe this is overkill, maybe I just clean the brick and then rinse really, really well to ensure no acid is on limestone.
I was just trying to think of a way to be more efficient. If I did not have to tape and plastic it would save a bunch of time as well as after rinsing, I will have to be very careful with the plastic having acid on it. I also thought about reducing the chem going into the grass. If a way existed that after I clean the brick, I could neutralize the acid while on the wall before rinsing, that would seem to eliminate having to tape/plastic, deal with the acid covered plastic after as well as reduce toxicity to the grass.
Do you have an efficient way to tape that long of a distance? This is just a thought but I have a hand masker that may help speed things up if you don’t have a way. I’m sure it would cut the red stucco tape. I have some at the shop i can try it out later and let you know. I just have a pretty busy day. I have to run out of state and try to get back in time for a visitation tonight. This is the hand masker I’m talking about. I’ve used mine for things from painting cars to masking windows and floors for applying Sheetrock texture. Never have had an issue. 3M Hand-Masker Dispenser - M3000 https://www.amazon.com/dp/B0002YQ7HO/ref=cm_sw_r_cp_api_i_OgOFCb24F1MME
I do have a hand masker and using the tape and plastic sheeting was one thought I had. I am going to try to do 200 ish feet per day and see how it goes. I figure 6 days give or take to get it all done. Maybe quicker. In my experience with limestone, sometimes what you think is 2 hours ends up being 3. I want to set expectations really low, so if I am moving faster, great.
