crap a moose

If you are going to solder on that copper, you need to clean it off. Fine scotchbrite, sand paper, pencil eraser, etc. Clean off any abrasive after, and use alcohol last.

I often use a flux, available at any welding store called "No corrode". It is safe on electrical stuff, and I sometimes use it on joints that are difficult to clean.

ALWAYS use solder designed for electrical use, and NEVER use acid core (plumbing) solder on electrical work. The solder that Radio Sh$$ sells is , ...........OK