Orange in concrete. (Not rust) needing help with ideas on how to remove & what it may be

Hey everyone. This is a commercial property we do. They’ve had these stains since the property was built. I’ve served them for almost a year now but before me, the general manager said he went through 3 other pressure washers & they all tried and failed to remove these stains. So we never discussed it after that & I’ve went on to service all other parts of the property. However, recently I got a wild hair up my rump and decided that I was going to remove these stains & increase my knowledge. I tried oxalic acid, which is my cheap go-to rust removal, but it didn’t work. This is all I’ve tried, right after my last visit. However I took these pictures in hopes someone here might have some ideas for me to try during my next visit in 2 weeks. Thanks in advance!

I just got back from an estimate, so I will take a stab. Did you try f9 barc? Oxalic is a weaker acid than what is mixed in f9, pretty sure without looking at the sds that it has stronger acids in it.

Irrigation runoff, iron in water, continually pools across that area (s). It will never go away until they fix the water issue (divert or treat).

I guess you’re referring to the stones around that area bringing in iron and other mineral deposits Dirtyboy? That would make sense. I never thought about that. I’ve got 1 gallon of F9 left. I was saving it for battery acid stains from golf carts but I guess I’ll give it a try on these stains. They’ve been there since I’ve started as mentioned & because of that, I’m trying to think if they’ve got worse. I honestly couldn’t tell you. Anyhow, thanks Dirtyboy. I’m going to give F9 a shot.

Even though I own the product. Admittedly, I’ve only ever used it for battery acid because of the price. Do you have a dilution ratio in mind off the top of your head for something like this?

i use it like the cookbook says. The iron wouldn’t necessarily come from the rocks, it comes from water that has iron in it, usually iron in water from irrigation runoff or sprinkler systems. You would see it in other places too.

Like I said I was just taking a stab at it, I’m not there. I would talk to a couple of others on here before I wasted my f9. Iron/rust stains can also be in concrete because the mesh or rebar they used is rusting internally. Who really knows, the apprentice could have left a shovel or trowel in the pour. You would be surprised at what you will find in old concrete when you bust it up. I found lawn chair parts in one old pour at my house.

They won’t come out. No sense in trying really. Read some of the old concrete threads on here and you’ll know why


Wow a lawn chair? lol, dang. Sorry for such a delayed response. I’ve been super busy with work as it is that season. I hope you & everyone else is staying busy as well. I’ll keep this short & just say, appreciate everything! I’m going to try the f9 you suggested at least once. Thanks again. Keep hustling.

Isnt it due to the curing process of the concrete? Where they layed down plastic or burlap while it cured and it somehow messes with it?

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That’s what I think happened.

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