soldering
I have repaired this circuit from a fridge but the soldering that I have marked in red seems to have pulled away from the copper track. That is because when I tried to replace the capacitor that was there, I had to pull and that was the problem. I have almost cut the track.
The circuit is now working, but I don't know if I can repair this in some way.
Regular solder is a mixture of lead and tin, so chances are that, yeah it would stick to actual tin.
Be aware that most of what is today called 'tin foil' is really made of aluminum. You would have to work at it to find tin foil made of real tin.
Aluminum is notoriously difficult to solder to, almost but not quite impossible, in fact. Basically you have to exclude oxygen from the surface you intend to join, which is easier said than done.
As regards actual tin, you should be able to solder to that, since most common electronics solder incorporates tin as part of the alloy. Pure tin will melt at a higher temperature than solder, since the alloy has a lower melting point than any of the individual components, so the joint should actually be a solder joint and not a weld.
Solder bridges mean you need more/better/fresh flux.
(Either iron or hot air will work fine. Heat is heat. I prefer iron for clearing shorted pins: wipe iron on sponge, apply to pins, repeat. The excess solder will stick to the tip.)
Best Answer
Make sure that any components that are attached to the pad are attached to the board in a mechanically sound manner. A little dot of epoxy glue or hot glue should do. You'll have to use your judgement.
Then make sure that the trace has enough copper to carry the current it used to. Use your judgement -- usually this is repaired with a bit of bare wire, or copper foil.
If it won't move, and it won't burn up, you're done.