Phosphoric acid is in Coca Cola

http://www.snopes.com/cokelore/acid.asp

From about 1/2 way down the page.

"FYI:

1. The active ingredient in Coke is phosphoric acid. its pH is 2.8. It will dissolve a nail in about 4 days.

2. To carry Coca Cola syrup (the concentrate) the commercial truck must must use the Hazardous material place cards reserved for Highly Corrosive materials.

3. Distributors of coke have been using it to clean the engines of their trucks for about 20 years! Drink Up! No joke. Think what coke and other soft drinks do to your teeth on a daily basis. A tooth will dissolve in a cup of coke in 24-48 hours."

-------------
To tell you the truth, I have even used it as toilet bowl cleaner. I also poured coke into the spark plug holes to break the pistons free an antique tractor engine that was stuck for 7 years. Let it sit overnight, then pulled the heads and whacked the pistons with a really big mallet. Within 2 days I had the tractor running.