Correct, soldering irons typically have iron-plated tips with a copper or cupronickel alloy core. Copper alloys with molten lead (which is why tin/lead is used as solder) but iron doesn't. Sandpapering away the coating will basically destroy the wettability of the tip. It's best to just wipe any dross or flux residue away on a wet sponge. Any embedded gunk can be gotten rid of by tip cleaning compound - a mix of flux/solder in a hard matrix that allows you to immerse the tip in a molten cleaning solution.rpdom wrote: ↑Fri Jan 18, 2019 2:29 pmThis I'd strongly disagree with. Most soldering iron bits have a protective coating. Sharpening them will remove this coating and expose the unprotected core which will rapidly degrade through use.
Lead-free solder will degrade iron-plated tips far faster than tin-lead solder.