Re: what happens if battery acid (conc.sulfuric acid) comes in contact with Al?

Hi There!

Yes You are correct in suggesting that there is a layer of Aluminium Oxide 
covering the Aluminium. This will act like a base in the presence of a 
strong acid.

          Acid +      Base       -> Metal Salt         + Water
Sulphuric Acid + Aluminium Oxide -> Aluminium Sulphate + Water

With dilute sulphuric acid there may not be sufficient 'strength' to react 
with the Aluminium Oxide layer, but concentrated sulphuric acid (Dangerous 
Stuff) will definitely react with it.

If there is sufficient sulphuric acid present to react with all of the 
Aluminium Oxide layer, then there will be a reaction with the Aluminium 
underneath. This will be lot faster reaction than previous and will produce  
hydrogen.

Sulphuric Acid + Aluminium -> Aluminium Sulphate + Hydrogen


Hope this Answers your question.

PS Battery acid is very dangerous. Any contact with skin..Immediate 
irrigation for 15 mins. Eye contact...Get to a hospital!