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This question already has an answer here:

I can't tin the iron properly, because feeding solder onto the tip has it flow downwards and collect into a blob before splitting off and creating a mess.

My iron may not be calibrated. And I don't know how to measure its temperature without a device to do so (I only have a multimeter). It is supposed to go from 250 Celsius to 450 Celsius (840 °F), but I can only solder onto the pad quickly at 450 °C. The solder melts at around 300 °C, but it doesn't flow quickly.

The iron I use is the T12 type.

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marked as duplicate by Nick T, Enric Blanco, Voltage Spike, Wesley Lee, Dave Tweed May 16 '17 at 22:05

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    \$\begingroup\$ Google "tinning" ... the oxide layer on the tip is stopping the solder from flowing on the tip. instructables.com/id/Soldering-101%3A-Lesson-1%3A-Tin-the-Tip \$\endgroup\$ – Spoon May 15 '17 at 11:55
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    \$\begingroup\$ Try electronics.stackexchange.com/questions/52879/… \$\endgroup\$ – Spoon May 15 '17 at 11:58
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    \$\begingroup\$ soak it in a mild acid (vinegar, coca-cola, saliva) overnight, then scrub w/steel wool, then coat with flux and turn on to the highest temp for 10 mins. then treat as new. \$\endgroup\$ – dandavis May 15 '17 at 13:41
  • \$\begingroup\$ It's barely used. This is a new iron. Did I overheard it? \$\endgroup\$ – Altoban May 15 '17 at 14:43
  • \$\begingroup\$ -dandavis, on another older iron, I dipped it into a small solder paste cup, and turned on the heat. The paste which looks like lotion, boiled and the iron too came out clean. I don't know if this is right or not. Here​ is the paste : amazon.co.uk/BS-10-Soldering-Paste-Welding-Electronic/dp/… \$\endgroup\$ – Altoban May 15 '17 at 18:04
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It's possible you've damaged the plating on the tip. Try wiping the tip on a damp (not sopping wet) sponge and tinning again with fresh electronic grade flux-core solder. It should look like this before you add more solder:

enter image description here

The site I scarfed the above photo from mentions using sal ammoniac from your nearest Indian grocery store as a last resort. Even if it fails, a nice chaat, bhel or paan can't hurt.

enter image description here

If the tip remains stubbornly black and not shiny tinned you may need to replace the tip. You should keep a few different sizes of spare tips on hand anyways.

Don't use a good soldering iron tip for things like melting plastic- it will ruin the tip and may result in toxic fumes.

Most modern tips are copper, plated with iron, plated with tin (the metal). If the tin plating is damaged, the tip is 'done', since iron does not readily wet with solder. You can file off the iron plating in an emergency and use the tip for a while but the solder will erode the copper away in no time (relatively speaking).

You can measure the soldering iron tip temperature using a type K bead type thermocouple- many multimeters will accept such a thermocouple. Just immerse the bead in the solder, it will be close enough for this purpose.

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    \$\begingroup\$ Spot on. A copper tip will get you out of a hole (and you can make a fine tip by wrapping solid wire round a cold iron) but it won't last. I've had some success rehabilitating a neglected iron with some fine wire wool, but even then you're probably at the "order a new tip" stage. \$\endgroup\$ – Chris H May 15 '17 at 13:31
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    \$\begingroup\$ Chris has a good suggestion- especially if you have bronze or brass wool around (used shipboard, for example). In most marine shops it will cost more than a new tip though. Brass and bronze are soft enough that they don't add to the damage. \$\endgroup\$ – Spehro Pefhany May 15 '17 at 15:26
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    \$\begingroup\$ Yeah the brass "sponge" style cleaners or even a brass wire brush are great for fixing badly oxidized tips because the brass is harder than the oxidation layer, but softer than the coating on the tip itself. You just have to be careful because sometimes you will get a brass-plated steel brush which will ruin the tip. Basically, just avoid the really super-cheap brushes and you'll be fine. \$\endgroup\$ – David Freitag May 15 '17 at 18:50
  • \$\begingroup\$ +1 for the brass wire brush. I couldn't find any brass wool in stores around me but brass brushes are easy to come by. \$\endgroup\$ – 0xcaff May 15 '17 at 23:13
  • \$\begingroup\$ I can't easily buy non-steel wire wool but have a brass bush. The sort sold for suede should be real brass all the way through but you can test with a magnet (@DavidFreitag). \$\endgroup\$ – Chris H May 16 '17 at 8:48
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Spehro Pefany has good advice but I'll add that there are "tip activators" that will clean off the oxidation surprisingly well. This Weller is the only one I've tried but it works wonders.

enter image description here

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  • \$\begingroup\$ Please take care and hold your breath while doing this. :) \$\endgroup\$ – Franz Forstmayr May 16 '17 at 21:23
  • \$\begingroup\$ Oh yeah, it does smell awful and I'm sure it's full of terrible chemicals! \$\endgroup\$ – kkemper May 16 '17 at 21:25
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My soldering station includes, besides a Weller iron with temp control & a fat roll of solder: flux, and a gold R2-D2-looking thing that has steel wool. https://www.amazon.com/Welding-Soldering-Solder-Cleaner-Cleaning/dp/B00PQ32CUW/ref=sr_1_1?ie=UTF8&qid=1494968675&sr=8-1&keywords=gold+soldering+iron+cleaner

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