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.

Solder Metal Contact

  • 1
    \$\begingroup\$ For soldering to large metal object the temperature is less important, the wattage is. I have a special 100W soldering iron for that sort of stuff (Big cheap thing with a huge copper tip.) \$\endgroup\$
    – Oldfart
    Commented Sep 14, 2019 at 18:16
  • 3
    \$\begingroup\$ You may have sanded off the solderable plating on a steel part. You can try a much more aggressive flux such as that designed for stainless steel soldering, but you'll have to clean it off very thoroughly afterward to avoid corrosion. Or just get a new part. Looks like you've damaged the plastic on that one anyway. \$\endgroup\$ Commented Sep 14, 2019 at 18:22
  • \$\begingroup\$ I suggest a flux from a plumber’s box - but again you have to wash it off after - and a decent size iron... those are the solutions... \$\endgroup\$
    – Solar Mike
    Commented Sep 14, 2019 at 19:04

1 Answer 1


I fixed it, I just wrapped the wire around that metal contact twice and soldered it and now it is fixated on strong enough that I cannot pull the wire out with medium force.

Thanks for the comments/tips!


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