Cleaning Concrete Stains?

[zwiller]

I am a handy guy and can fix mostly anything but for some jobs it's best to call a pro. They have the chems and tools and most important they have experience. IE I had some really bad carpet at a rental and was ready to pull it but my Mom suggested to at least try a pro first, even though no one in my family had ever hired a carpet cleaner before, we always just rented the machine. So I do and to all of our surprise, the carpet was basically like new when it was done! For DIY you are gonna need acid like SmokinAl said. Muriatic/pool, citric, oxalic. I would then follow up with a base cleaner to neutralize like pool shock/SH injected into a power washer with a surface cleaner attachment. As already mentioned, you are looking at a reduction at best.

 

[Jabiru]

I have used Kitty litter (the sand) multiple times, leave it on for a few days. Then soak it with 1 part chlorine 3 parts water. Keep it wet with that for a few hours. Pressure clean.

 

[forktender]

A torch is not going to do a thing to a rust stain. Wet the surface then sprinkle TSP powder on it. Let it stay on for a day or two moisten it and scrub with a wire brush. If that don't work try Lime away and a wire brush. Wear rubber gloves and safety glasses.

 

[tsapp]

Try oxalic acid wet the area sprinkle a fair amount on work it with a brush a little. let it sit a few minutes and then rinse it off. Don't let it dry on there better to do it on a cooler or cloudy day. so you can let it sit longer. You can put a tablespoon or two of this stuff in the back of a toilet and let it sit a while and then flush and the inside of the tank will look brand new. also works great to get rust stains out of a dishwasher.

 

[bill1]

Thanks. Oxalic acid is good on rust stains. I'll have to try it for oil and grease stains.

 

[zwiller]

I'd apply a stripper with pump sprayer, let dwell, and then follow up with PW with surface cleaner attachment. https://www.restore-a-deck.com/RAD-Stain-Stripper.html

 

[bill1]

I've got a 40x60 that used to be a marijuana grow...they made a real mess of the concrete floor. I'd love to pressure wash the entire thing but I can't get my drywall wet. I've tried mopping with some simple floor cleaner, but I can't really scrub as hard as I need to with the mop. The floor looks like it was sealed, to begin with, but a lot of that has flaked off, even though it's only about 2 years old.

What should I use to clean this floor....without making a huge, wet mess inside?

Maybe just paint it? (Sealing is cheaper, but if it had a prior coating that's flaking off, I don't think that wil work.)
Are you worried about odors or just looks?

 

[chp]

So from the chemistry side, rust is an oxidized metal, to get the oxide broken up again, a reducing agent will do the trick. Formic acid, oxalic acid, sulfites are examples of a reducing agent. Just check the label on the rust removers. The challenge is that there is likely other things in the concrete that will also react.

Changing the pH with acids and bases can also put the oxide in solution and allow you to remove it, but it does the same thing with your concrete. So, you can try laying a rag over the stain and soaking the rag with the reducer or acid/base to increase the contact time, then after the rag starts to dry, remove it, pour on some kitty litter, grind that in to absorb everything, sweep it up …and repeat, just do some small test runs to see how it affects your concrete.

 

[bill1]

Guess I haven't grown enough pot...what do we think has stained the concrete? Chlorophyll? Drained steer manure?
If you've only tried a mop so far, consider renting a commercial carpet cleaner that has a large round (18"?) rotating bristle brush. They can do a lot of scrubbing with a minimum of water since you're worried about splashing on the inside walls.

 

[boykjo]

I dont recommend heating concrete with a torch. If it has moisture in It, it can explode.

 

[mike243]

grind the surface, the stain is embedded into it, a hand grinder if a small spot or a stand up model if a large area. after clearing it out clean and seal with a quality sealer to help prevent this