Juan's Metallic Mystery

It is impossible for us to answer every question and email we receive (especially technical ones).

But occasionally I like to share questions here on the blog and see if our informal "science community" can help.

The latest puzzle comes from someone named Juan....

His email is as follows (and for the record, we DO NOT condone the opening of batteries!):

I opened a 'Super Heavy Duty Battery' , to get the Zinc, Manganese Dioxide and graphite. After doing that I found a piece of metal and I do not know what is that, here are some properties I experimented:
- Bad Conductivity of Electricity and Thermal.
- It is light and it is a sheet.
- It does not melt at 700 - 900 K , when I heat it, it seems to form some kind of Oxide on the metal and I can get rid of it easily.
- It does not react with HCl.
I thought it to be an alloy but these previous properties made me think of Titanium, but it is quite expensive so it would be strange.
I hope you can help me. Thank you! And very interesting videos.