Dwell time for oil on Concrete???

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powerwashing4u

New member
I plan to wash some concrete with oil stains with Sodium Hydroxide (caustic soda beads) and TSP (Tri-sodium phosphate) mixed with 12% bleach. Oh, and of course heat! The thing that I want some feed back is what dwell time would you suggest???

PS. It has some rust stains that I will hit with acid first.
 
Commercial. Auto parts store; many vehicles that leak oil. Also, I will be using a surface cleaner. I have done many Residential driveways but fewer Commercial flatwork jobs.

I want to test out rekrete but not on this job. I forgot to mention that I follow up with Oxalic acid and then rinse. Has worked really well for me.

My issue is that I may be wasting time letting things dwell too long, so I was looking for some guidence.
 
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When I do this sort of work, I prespray it with a pump sprayer, starting at one end, and going to the other, and then start immediately with pressure washing it. If the degreaser is almost dry, it is usually perfect, and it dries pretty fast here.
I don't do all the other steps with Oxalic, etc. I still get good results.
 
Geez, I was not very detailed in my description. I apply the soap mix with a sprayer as well but I usually wait 15 to 20 minutes and then hit it with the surface washer, rinse, apply the ox and then rinse a bunch more. Thanks for the response.
 
caustic is a degreaser so I dont know why someone would do it that way especially since the caustic is a potentially stronger base depending on how strong the streangth


as far as bleach I cant imagine what that would do if anything to improve what the caustic does, and if someone were gonna use oxalic after the fact , that would sure brighten it enough
 
There was some black mold from a nearby tree so I thought I would ensure that is taken care of by using the 12.5%. It is a sidewalk and cement pad combo job, the ox is used on the sidewalk only to brighten it up. I really need to give more details when asking for help.

What amount of caustic do you recommend for a 5 gal mix???
 
Surfactants make raw ingredients more effective. You can use less beads in your mix if you have something like Dawn in there too. It helps to break the surface tension of the water, so the beads can be more effective.

It is not always how much sodium hydroxide in in the mix, but also what is in there to make it work. Leave your bead mix the same and add 1 cup of Dawn and note the difference. As always use caution in mixing your own chems and know your MSDS ahead of time.
 
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