Redeem code
 

I wanted to know what the redeem code button is there for in the new icon in the treasure chest.

Probably the same button that used to be in shops. As of yet there are no codes for free stuff in Pirates. However, it has been used in the past, I think, for the Kracken tattoo from the Call of the Kraken game. It may also be that they are reserving the right to add codes in at a later date, as both Cars and Pixie Hollow have codes for free items at the moment. Then again, this is D, and it could just be nothing. :D