2 suggestions (I am also an irrepressible bargain hunter and *always* buy the cheapest iron I can find )
1) have already met poorly designed, way too hot irons, tame it with a diode in series (an 1N4007 works fine).
In fact I have a dedicated outlet with a switch in series with the hot pin and a diode across it, so it's FULL/HALF .
The original idea was to keep the iron preheated between jobs, but later I found some nervous ones did solder quite well on the HALF position, flipping them on FULL for pot body soldering and such.
Try it.
2) that factory probably used chrome or nickel plating with a formula more suited to *decorative* surfaces than soldering iron tips.
Maybe the clueless plater gave it a "passivating" bath, excellent against ambient humidity or a saline atmosphere (I use it myself on my speaker frames, excellent bright, shiny and durable finish) bit probably too tough for mild deoxidant rosin.
*IF* you have some available (drain pipe cleaner) submerge in it the suspect tips , just the 3/8" inch conical tip section you want tinned, wait a minute (should be more than enough) and rinse it well in running tap water.
The idea is to "eat" just the thinnest amount of coating, leaving most behind for protection.
Then tin as I suggested earlier, starting from cold.
It *should* work.
FWIW once no Long Life tips were available (one of our Trade Crisis) so I bought one meter of 5 mm Brass rod (same diameter as the *real* tips).
My homemade tips worked like a charm and lasted a lot.
The usual pure copper tip dissolves in liquid tin ... but brass is already *saturated* in it, so it goes on much slower.
Long life tips are often covered in iron (check it with a magnet) which is then plated and tinned.
A complex process, some friends got into it (making replacement tips when no originals available) and failed, had lots of stuff back.
1) have already met poorly designed, way too hot irons, tame it with a diode in series (an 1N4007 works fine).
In fact I have a dedicated outlet with a switch in series with the hot pin and a diode across it, so it's FULL/HALF .
The original idea was to keep the iron preheated between jobs, but later I found some nervous ones did solder quite well on the HALF position, flipping them on FULL for pot body soldering and such.
Try it.
2) that factory probably used chrome or nickel plating with a formula more suited to *decorative* surfaces than soldering iron tips.
Maybe the clueless plater gave it a "passivating" bath, excellent against ambient humidity or a saline atmosphere (I use it myself on my speaker frames, excellent bright, shiny and durable finish) bit probably too tough for mild deoxidant rosin.
*IF* you have some available (drain pipe cleaner) submerge in it the suspect tips , just the 3/8" inch conical tip section you want tinned, wait a minute (should be more than enough) and rinse it well in running tap water.
The idea is to "eat" just the thinnest amount of coating, leaving most behind for protection.
Then tin as I suggested earlier, starting from cold.
It *should* work.
FWIW once no Long Life tips were available (one of our Trade Crisis) so I bought one meter of 5 mm Brass rod (same diameter as the *real* tips).
My homemade tips worked like a charm and lasted a lot.
The usual pure copper tip dissolves in liquid tin ... but brass is already *saturated* in it, so it goes on much slower.
Long life tips are often covered in iron (check it with a magnet) which is then plated and tinned.
A complex process, some friends got into it (making replacement tips when no originals available) and failed, had lots of stuff back.
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