On 6/12/2011 2:16 PM, Home Guy wrote:
Steve B wrote:

From the looks of it, it has been on there for quite a while. What
is the best way to get that off?

Acid will remove hardened concrete from lots of different surfaces.

I remove concrete residue from ABS plastic textured form liners (4 ft by
10 ft) by spraying concentrated sulphuric acid on them using an ordinary
hand-held spray bottle. This is the suphuric acid that's sold by the
gallon in stores like home depot, labelled as muriatic acid (I think
it's used for swimming pool maintainence).

I pretty much have to wear a mask and rubber gloves while I'm doing that
- the fumes will really mess up your nose even if you're doing it
outside. I spray it on full strength (no dilution) and let it sit for a
few minutes and then take a hand-held nylon (or some sort of plastic)
scrub brush to the surface. The concrete comes off like it's loosened
wet dirt. Nothing else can do this - no amount of elbow grease, etc. I
then spray it down with water and it all comes off like loose crud. The
spray bottle can't be used again - I think the rubber inside the trigger
gets messed up by the acid.

You can get concentrated sulphuric acid on your skin and it really
doesn't do much, but it will sting if it gets onto any scratches on your
skin, particularly around your finger tips.

I've also used the same acid to remove dried concrete from my 3-cf Red
Lion steel-drum electric cement mixer.

You can buy some really expensive concrete remover that may not be so
caustic to bare steel - I think it's just some other form of acid (might
also be similar to rust remover). They won't tell you on the label
what's inside. I think the bottle I had once was called "Concrete
Blaster".

Muriatic acid is hydrochloric acid. It is used to etch concrete and
will clean up the tools but could also attack the metal. Fumes and
liquid are both hazardous.