lemon juice is 6 to 10% citric acid. The hotter the lemon juice the faster the reaction rate.

The 'ancients' used a mix of lemon juice, pumice, beeswax and salt to 'burnish' their bronze, etc. armor and weapons to a mirror finish, the beesWAX to seal the surface from tarnishing.

In most navies of the world they use carbonated 'sodas' that contains citric - coke, pepsi, & most lemon flavored (lemon extract + citric acid) ... .