Why is brass resistant to corrosion?

[KAS90]

hey there..
I read that brass "an alloy of copper and zinc" doesn't corrode unless more than 15% of zinc is added..
My question is.. what is the reason behind the resistance of corrosion of brass? does it have 2 do with the electronegativity or sumthing like that?
I'd appreciate ur response and help a lot..
Thanks in advance..

 

[03myersd]

It would eventually corrode. But the way it works is that zinc is an electron donor. When the copper is ready to corrode, or oxidise (lost an electron), the zinc is there waiting to give it another to replace the lost electron. Obviously this cannot go on indefinately. Its the same reason why we get zinc coated nails etc.

As to why is corrodes if more than 15% is added... No idea.