Need help with my Oxalic/ rust technique

Hello I’m working on my own concrete to get experience.
Pictures are of a rust stain before. Wet with just water and after oxalic acid.

I used 8oz per 1gal the 1st time then upped the strength to 12oz/1Gal. I did not use any pressure just water hose and a push broom. Dwelled.

Must not be doing something right because the rust is still there and now that part of the concrete is too bright.
Thank you.

You want to pressure wash first to clean out the pores of the concrete so the chem can do a better job. Oxalic won’t work on real bad rust. That’s when you pull out F9 Barc.


It if he pressure washes it, won’t that take off the cream coat?

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Make sure you mix it well. It doesn’t dissolve well. Use hot water and shake it up. Apply, dwell, apply dwell and keep going till it’s gone. I found brushing does help some.

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That’s a great question and something you always want to watch for. It mainly depends on how old it is. As long as it’s fully cured it should be okay. Most wait at least 18 months before pressure washing. You always want to keep an eye out for milky looking water though no matter how old it is. There’s plenty of subpar concrete work out there.


Thank you I will always remember that.

Thank you

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What’s going on with the concrete being so much brighter?

F9 products (better than regular oxalic) always recommend treating entire area as the treatment affects more than just rust. It ensures the side effects are uniform throughout the entire area. Just treat it all with oxalic and get it all brighter.

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That’s the problem I have using Ox on concrete. The results are inconsistent, even with brushing and multiple applications. My time is more valuable than the savings I get from using it, ie so I rather just break out the good stuff from the start and get it done.


I spent a lot of time on this one spot as well. Thank you for your post because I will be looking for some cobble oxhide or f9barc. I want to be the company that specializes in stain removal because my competitors are not

Thank you that makes sense

F9 Barc is the way to go :+1:

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