Cleaning rust off asphalt driveway

[Econdron]

Had this issue back when I worked out of my garage, one day I decided instead of sweeping up the grinding dust, I would just blow it all outside and let the wind carry it away. Didn't work as well as I had hoped. About a week later, I had a nice orange driveway. It was due for a sealcoating, so I just let them take care of it. Wasn't there when it was sealed, so I'm not sure if they went right over it, or if they cleaned it somehow. Well now my shop is in a multi-unit complex with a large asphalt parking lot. I've been careful about making sure minimal grinding dust makes it outside, but it appears now that someone used the shop floor fan, put it in the back of the shop (facing the bay door) and went to town grinding away. The front of my unit is now bright orange, and I'm worried the association will either fine me, or make me pay to sealcoat the entire lot. I pressure washed it this morning and that got a lot of it off, so it's not as bright, but still orange. Anyone know any tricks to cleaning off the rust off? Preferably something relatively inexpensive and quick, as this may end up being an ongoing process.

[Oldendum]

Oxalic Acid. Also known as "wood bleach", which is used in some wood deck cleaners. Not a really nasty acid like HCl, though precaution is advised. (Various vegetables like spinach contain some Oxalic acid.)



The scouring powder "Barkeeper's Friend" contains Oxalic acid if you just want to try some on a small scale. Pretty cheap at the grocery store or Lowe's or a place like that.

An alternative might be dilute phosphoric acid. Something like Calcium, Lime, Rust remover (CLR).

[aevald]

Hello Econdron, we use muriatic acid on our sidewalks and surfaces around our swimming pool, it works very well also. You can generally buy it in 1 gallon plastic jugs and cut it with a little bit of water, spread it around, scrub a bit with a push broom, and then rinse it off. Good luck and best regards, Allan

[tapwelder]

Depending on how much you have try vinegar and a scrub brush. It will work just not as readily as muratic acid. Just kind of annoying having a jug of muratic acid sitting around. A couple week ago I used muratic acid to clean red chalk off stone. A few drops were needed and I have a gallon to keep safe in the shop. I would start with vinegar.

[G-son]

Citric acid dissolvs rust like oxalic acid. Sometimes available (for a good price) in descent sized containers among the spices in the stores, if they only have small containers the price gets too high.

[Econdron]

And these acids won't dissolve the asphalt at all? I remember a while back I tried cleaning some paint off the driveway with paint thinner and it looked like it was melting the driveway.

There's a pretty large area with lightly visible rust stains. Though only about 20' wide x 5' deep is it really bad.

EDIT: Did a little research, everything I'm finding says acids will dissolve asphalt. I can't find any rust removers intended for asphalt...

[Oldendum]

As far as I can recall, asphalt or tar is one substance that has been used as an acid resist. As in acid etching, even to the point of nitric acid, a mean one. Put tar on something, scratch a pattern and let the acid do it's work.

The world of "acids" is wide. They are not all stuff that dissolves anything in their path. I eat candy and food that has acetic acid in it. When I belch, I think what is in my stomach is hydrochloric acid. I think your parking lot is a bit tougher than that. If not, then move.

[b00mhower]

Do you have any pictures. I have a pretty good idea of what your talking about but it helps to see. Also I'd listen to these guys if I were you. Lots of good advice there

[Harry72]

How can you see rust stains on asphalt, its black isnt it... well it is in my country anyway , or are you referring to concrete?
IMHO, CLR is best for "rusty concrete"

[weldermike]

When i was young and worked alot on motorcycles in my moms yard she would yell at me for wrecking the concrete with rust stains and oil stains. I found this stuff called Acrysol. It came in a light green and white can. Worked perfect. Squirt it on the areas and push broom it all around, and then hose everything down and gone, like bran new concrete. Sometimes it took a few tries, but worked great. Not sure if its still around, but worth looking into.

[weldermike]

Still available and seems like home depot and lowes carry it. I just did some minor research and it came right up.

[mike837go]

Also look into a product called Iron Out.

[Sharon Needles]

Get some Rust Mort from Napa and put it in a garden sprayer, it'll turn the rust black so it blends in.

[hddnis]

Also look into a product called Iron Out.

Yep, mix it up in a five gallon bucket per label directions and it will take away all the rust stains without any fuss or bother.

Pour it on, then rinse it off. Rust will be gone.




Mr. HE

[Oldendum]

Super Iron Out Outdoor version contains Ethanedioic acid, dihydrate. Which is also called Oxalic acid dihydrate, the common form.

[BD1]

I was wondering if just get some flat black spray paint.

[dbotos]

Get some Rust Mort from Napa and put it in a garden sprayer, it'll turn the rust black so it blends in.

I was going to suggest phosphoric acid too, which is the active ingredient in Rust Mort. Also sold at Lowe's in Jasco Prep and Primer and Home Depot in Klean Strip Prep & Etch. Another popular brand is Skyco's Ospho, which I've heard of, but never actually seen in person.

As stated, it'll turn the rust to a black(ish) color (iron oxide changed by phosphoric acid to iron phosphate). Should do a good job on fairly thin stains that it can fully penetrate/convert. If there are "larger" particles still embedded in the asphalt, those may re-rust after additional rain and/or wear from traffic. Obviously test on a small area before going hog wild on the whole parking lot.

[nadogail]

I have diluted Henry's roof emulsion with a thinner or Gasoline and it made a cheap watery black paint that adhered well and covered dirt and stains.

[Excalibur]

Ever thought of flat black paint?


Excalibur

[7A749]

I have diluted Henry's roof emulsion with a thinner or Gasoline and it made a cheap watery black paint that adhered well and covered dirt and stains.

Yup. That's what you do RIGHT BEFORE you move out of the building

[Excalibur]

If the area is not too large take a propane torch and warm it up. Scratch the asphalt around with a rake or something and tamp it back with a plate tamp of some kind.


Excalibur

[ironmangq]

And these acids won't dissolve the asphalt at all? I remember a while back I tried cleaning some paint off the driveway with paint thinner and it looked like it was melting the driveway.

There's a pretty large area with lightly visible rust stains. Though only about 20' wide x 5' deep is it really bad.

EDIT: Did a little research, everything I'm finding says acids will dissolve asphalt. I can't find any rust removers intended for asphalt...

The paint thinner will definitely damage asphalt, asphalt is oil based and paint thinner is used to dilute and dissolve oils. Anything designed to emulsify and dissolve oil will breakdown the paving, as will gasoline and motor oil.

[Weldalittle]

Super Iron Out Outdoor version contains Ethanedioic acid, dihydrate. Which is also called Oxalic acid dihydrate, the common form.

I've used that on a lot of stuff. From concrete to PPE furniture. I've used many of the other homeowner rust removers too, but Super Iron Out seemed to work the best.

edit- wow, I fell into a thread revival! oops

[N2 Welding]

I was wondering if just get some flat black spray paint.

That's too funny that was my first thought...

[DealsGapCobra]

As this is such an old thread I would be interested to hear what you tried and how it worked?


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