The Lemon juice is acid, so it's the oposite of the leak, as someone told be. It will nutralize the leak. then you wait some time, and clean it with soap water. After the nail varnish will protect the area from oxigen, preventing corrosion, and other problems.
I was afraid that after all the work i could damage something, but it's working..!!!!
very important is to wait a few hours between each step, to give time to dry.

Next step put a CR2032 coin cell with a diode as replacement of the old battery. I order the CR2032 and a support for it, very cheap, i am still searching for the best diode for it.