https://www.eevblog.com/forum/beginners/brass-sponge-has-rui...
Anecdotally, all wool seems to accumulate abrasive crud, various amalgamated solder waste, melted plastics, and trimmed bits of steel etc.
Best of luck =3
The stuff that came with my (apparently genuine) Hakko 599B is non-ferrous (and is therefore not steel). Refills are Hakko part 599-029.
Soldering iron tips are usually made from copper with a thick iron plating. On Moh's hardness scale, iron doesn't care much about what brass thinks. :)
In situations where PCB ground pours removed thermal-reliefs for power handling reasons, mini-cartridge-heaters often simply don't have enough thermal mass to heat an area fast enough without the control-loop missing temperature ranges and or time limits.
Anecdotally, same reason good portable butane catalytic iron units are often superior to USB-C/battery operated units.
Note Zinc contact is restricted in some places, and that ban includes zinc-brass sources. Best of luck =3
The tip on my soldering iron is perfectly fine though.
AFAICT, it works well with all soldering irons. I certainly haven't noticed any detriment to my soldering irons over the >decade I've used it. It really seems to be fine and it sure is simple to use.
(I really have needed to buy new brass wool for a few years now, though. It works, but it is not nearly as slick-and-clean to use as it once was. Sourcing this from Hakko directly seems like a safe route and it's probably cheap-enough -- maybe I'll buy a few refills and have some for the rest of my life.)