A blackened tip means it has oxidised and as you are finding the slolder will not tin the tip. The oxide is difficult to remove but rest assured it can be done.Bandit Mick wrote: ↑Sun May 23, 2021 8:23 pm Thanks for the soldering advice Brian - useful as I am having real bother at the moment. Perhaps you or another member can help me. Just bought a new tip and after tinning 6 wires the tip will no longer hold solder and appears blackened. I’m using an antex 35w iron, 63/ 37 solder and DCC sapphic liquid flux. Don’t know if the solder is rosin cored but did buy everything from a very well known reputable model shop. I left the iron on for 20 minutes before using and clean with a damp sponge. Don’t laugh, but this is my 4th tip in as many years. What am I doing wrong?!!!!!!! Any help much appreciated before I throw the iron in the bin and stamp on the layout and give everything up as a bad job!
The first thing to try is to try one of those tip cleaners that looks like an unravelled brass Brillo pad in a some canister. You may have to rub the tip through quite vigorously for a while. If that does not work if you have a Dremel like tool then using a BRASS wire brush will shift it eventually, alternatively use one of those brass hand brushes used on suede shoes.
I have highlighted the word BRASS as the tip is coated with iron carbide and you must not use any abrasive that will cut through that. Cutting through the coating will expose the underlying copper and for a while your iron will solder well but eventually you willl find a cavity appearing and it will need replacing.
The iron carbide coating is the reason you are having the problem in the first place. On brand new irons and tips the tip being iron carbide coated can rust if moisture gets to it. To stop this happening manufacturers coat them with I suspect a varnish or lacquer, this needs to be removed before use to avoid the issues you are having. A wipe with a IPA soaked cloth should remove it.
When tinning your iron as it is warming keep trying to tin it before oxides form once flux appears on the tip (smoke emanates) you will be OK and eventually solder will melt and adhere. Wipe on a damp soldering sponge to leave a thin shiny surface and get into the habit when soldering to wipe the tip each time you pick up the iron. An alternative method but creates toxic fumes and needs to be done in a ventilated area with some sort of extraction and that is to quickly dip the tip as it is heating into the flux and tin immediately. Works every time but comes with a warning