dried paint off of concrete

[RotBaron]

Have paint drops and splatter all over parts of concrete where sloppy handyman built our carport. The paint has been there at least 2 years at this point maybe longer.

So far I've tried:

-paint thinner; didn't work

-muriatic acid (as suggested by an Ace Hardware agent) nope, but it did take many layers off that I'm not sure was good for the driveway in long run. The Ace guy said muriatic acid would work better than turpentine...

Any suggestions?

[NatCigg]

<<<< knows nothing 

sandblast? the damage from sandblasting may be less than chemical alternatives. 

[ghi]

 gasoline, methanol , scratch it with sandpaper or burn it ;

[smoe]

Some type of chemical car paint stripper might do. I have never tried it on concrete and couldn't say if it would do any harm.

[pembquist]

Did you already try power washing?

[morfiend]

  I know it sounds silly but if it's a small area try some brake fluid.  Now it may leave a stain so test an area that wont be seen!   If you've ever spilled brake fluid on a painted part you'd know what I mean.


   The rumours of having brake fluid accidently spilled on my car by an old girl friend are completely untrue..........




    

[Easyscor]

Power wash.

Rent one. Check with Home Depot's rental department.

[smoe]

gasoline, methanol , scratch it with sandpaper or burn it ;

Actually, a propane torch may be worth a try. Just lightly heat the paint and see if it peals off.

[68valu]

I have used this: http://www.coppergreen.com/greensliquid.htm

mostly on wood furniture, but it should work on concrete as well. use a TSP solution for rinsing the concrete after removal.


                                                                                                   68valu

[WEZEL]

Actually, a propane torch may be worth a try. Just lightly heat the paint and see if it peals off.

I would not use a torch, the moisture in the concrete will expand rapidly causing it to pop  into sharp flying objects.......I made the mistake of heating up a U-joint on the floor and had to pick about a dime sized chunk on concrete out of my cheek........not fun at all 

[HL117]

SKYDROL

[Hoarach]

If you can find any, hydrocholoric acid would probably do the trick.  In undergrad school built a brand new $50m science building which the dean of the biology department wanted to keep the facilities cleaned.  Some of the stains used for various slides would get on the floor due to incompetent students and as the TA, had to somehow get some of these stains off the floor.  Anyone that has handled biological stains know how much of a pain in the arse they can be to get off anything, can take 1-2 weeks just to get off skin.  Used 2M HCl and it took everything off real fast.  Dont just get 1M HCl if you can find it, make sure it is concentrated to at least 2M.  For the heavy stains used 5M HCl.  Be sure to wear gloves when handling it if you do manage to find it.  100% ethanol would probably do it as well as a safer option.

Edit: Duh didnt read you tried muriatic acid which is HCl but probably isnt concentrated enough being its bought in a hardware store and its not science grade.
http://www.sigmaaldrich.com/catalog/product/sial/258148?lang=en&region=US
http://www.sigmaaldrich.com/catalog/product/sial/84422?lang=en&region=US

[Easyscor]

There's a lot of bad advice in this thread. Concrete is not indestructible. Get it wrong and you'll be replacing it when the top surface rots.

[ROC]

Do you have pictures of the area?  Is it a thick layer of paint or was the original spill/drip cleaned up and you are dealing with the paint that absorbed into the concrete?
Concrete is porous, soaks stuff up.  It's old, which means it's going to be tough.  Pressure washing is your best bet, but you have to be extremely careful as you can cut the top, smoothed layer of concrete right off and expose the aggregate underneath.  If it's a wide area, maybe you're better off coating the area instead of damaging the concrete.  Nice outdoor concrete coating, sand or earth colors.  Might dress the place up and solve the spots at the same time.

[RotBaron]

OK thank you gentlemen for the responses. It does appear as though even that muriatic acid has taken a layer off the top and as said exposed the under aggregate. I won't be experimenting in anything but tiny areas.

The areas with paint are drops and in some spots heavier, like the painter didn't get the brush to wood in time after it was just dipped. The concrete is very old, like 30yrs maybe, maybe more, but has been well kept over those years.

I might try some of the suggestions on single drops to see the result.

Could gasoline really be effective if paint thinner was not?


TY
Rot