How To Fix Oxidized Solder Tip
Try not to leave the iron sitting hot on the bench while not in use.
How to fix oxidized solder tip. Turn it off as soon as you have finished soldering. Sharp till it gives you a shiny look. Use brass wool or specially designed cleaners on the tip.
The heat will activate the flux and start the chemical reaction that will remove the oxidation. Just like with sandpaper you must tin your soldering tip after cleaning to prevent prolonged oxygen exposure. The tip gets black and solder is not sticking to it anymore.
And move the tip after applying Solder on that unless it gives a shiny finish. Turn off your soldering iron. Lastly clean it again.
The best tip tinner is your solder--tips should always be coated with a small amount of solder. The main motive is to remove old flux or Solder. The problem here I believe lies with the soldering-tip temperature.
This means that after every soldering operation you clean your soldering tip dry wet and then tin it before you put the soldering iron back in the tool holder. If you want to clean it before using get alcohol and a piece of clean cloth then with their help remove contaminants from the solder. Extended use of soldering tips at high temperatures can easily lead to oxidation.
It took a lot of effort with tip tinnercleaning compound to make the solder wet the tip again. Good soldering process is important. If you are not going to solder for 3-5 minutes.