How do steel plated soldering tips wet solder so well 1

[renzokuken01]

Not going to deny it, I'm not an Materials Engineer or any Engineer that deals with hardware. Well... I can be called a Software Engineer, but I have a question that is in the Material Sciences.

I want to know how modern iron plated soldering tips wet solder so easily. I know that under the temperature the soldering iron is at (~180-220°C), the iron or steel passivates and it's pretty much impossible to get solder to wet it. I've noticed that even if I don't pre-tin it, there's a bit of solder that seems to leak out of the iron surface, so all I have to do is keep wiping it. So how does it do it?

 

[racookpe1978]

Are you trying to solder two iron surfaces, or asking about the coated (tinned?) iron tip on a soldering iron being used to join two copper wires? (My home soldering gun is not iron-tipped, so I'm not going to address your question directly. Very, very old soldering irons were furnace or torch-heated, then moved to the solder joint.)

 

[berkshire]

The iron coating is there to prevent the tin from eating away the copper core of the Soldering tip, the iron is somewhat porous and can absorb a tiny quantity of the tin , so when you clean your iron that residual tin will come to the surface. If you clean too much you will remove all of that tin and you will have to re-tin your iron from scratch . This is done by abrading the surface on a sandpaper like surface until all of the impurities are removed, then fluxing and re -tinning the surface. see the attached PDF on the care and feeding of soldering tips.
B.E.

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