Removing stubborn stains from concrete

[derekcaldwell]

I have a job to remove stains from the back side of a shopping center. These stains are in several areas. Some of them are caused by the roof drains going into the parking lot. Some are nasty run-offs from the dumpsters. But there is a certain area (pictures attached) where the stain was caused by what I don't know. I tried using 4 chemicals in these areas with no success. I used All-Brite and Power House from Sun Brite Supply. Both of those are butyl based degreasers. I then used Zep Concrete Cleaner. And finally after those failed I used ProBRC from Sun Brite Supply. That has Hydrochloric acid in it. None of these worked. Does anyone have any suggestions? If it can't be cleaned what is the next best course of action as far as informing the client of expectations?

 

[whit49]

The stains appear to rust stains, from what I can see in the pictures. Two weeks ago I did a concrete job for a customer which had rust stains on the concrete. I used Aluminum Brite, full strength, and my cold water 4000 psi machine. I got 100% removal. Customer overjoyed!
Sprayed Aluminum Brite, waited 10-15 minutes, then hit it with cold water, it worked!

 

[Bleemus]

If it is rust Oxalic acid should get rid of it. If it is battery acid it won't come out although some claim that Prosoco Ferrous Stain remover gets out battery acid burns but I haven't tried it.

Here is a picture of Oxalic on an irrigation rust stain. Mixed 1/2 lb to a gallon.

 

[Mark]

Derek,

It will take a strong acid like muratic, or hydroflouric.

Be careful!

 

[derekcaldwell]

Thanks for your help guys. I will try all of your suggestions and reply back. I am glad I have this network for help. Maybe a few years down the road I can actually give some advice.

 

[john orr]

I would definitely go with the Prosoco Ferrous Stain Remover. It runs about $28/gal and should be available at your local brickyard.

 

[itswillist]

the oxalic acid works for me ..