mikesewell said:
Yup, you're right. Muriatic acid, it's diluted hydrochloric acid, be careful.
Yep, it'll clean concrete very well.
Be careful is right, it's deluted hydrochloric acid, but you'll still have to delute it even more with water.
About 20% muriatic acid to 80% water(about 1/4 gallon acid to six gallons of water), if you put it on straight you won't have any concrete left, you won't have a happy customer either.
And pour the acid into the water, not the other way around.
Fill a large bucket close to full with water, then add the acid, wear rubber gloves, safety goggles, and old clothes.
Even deluted the stuff will eat holes in your clothes, not when it gets on them, but after you wash them, they'll have holes in them anywhere you got the acid on them.