I want to solder a wire onto this metal contact, but the solder wont flow into the contact. I have my soldering iron on 300 degrees Celsius using a chisel tip using 60/40 rosin core solder. I sanded the metal contact because it was corroded. I kept the soldering iron on the metal contact for 10 seconds to heat it up, but it still does not work. I have tried using Rosin Core Flux Paste.
What should I do now?
Edit: I increased the temperature to 400 Celsius and now the solder is melting on the metal contact, but it balls up onto the metal instead of flowing.