I bet that glob is JB Weld epoxy, which can contain iron and/or steel.
If it were truly pure steel, it would have to be molten in order to glob up like it shows in the pic. And steel has a melting point twice as high as aluminum, so it would leave burn marks on the aluminum, if not melt right through that thin sheet.
Again, I'd say to try grinding it out of there and see how it goes.