Grease in machine

I'm still working on partially restoring my old Westinghouse 102.  When I removed the inner galvanized cooler box and the insulation between the inner box and the outter metal chasis I've found lots of grease smeared inside of the machine.  It's mostly in the corners and joints of the sheet metal. I've had to remove the grease in order to treat the corrosion.  What was this grease for?  To seal the box like caulk?  To hold the insulation in place?  To help prevent corrosive? All of these?  And when I put things back together is there a special grease or other compound I should use?
Anyonehave any idea what I'm talking about?

Justin