How do you tell you can weld this metal/bolt/part

[AndyAndyAndy]

I have MIG welder with flux core wire.

Often I'm not sure if I can weld some part/bolt/nut/piece of metal from scrap pile. I was trying to use magnet, this method somehow works. I'm also aware that welding some stuff can make dangerous fumes. How can I tell if I can weld it. And if it might be dangerous?

 

[jamyers]

If it's galvanized (silver colored zinc coating), the fumes from welding are poisonous.

Otherwise, the only way I know of is to do a test weld and see.

 

[JTSpeedDemon]

^^Generally, a shiny finish means its zinc plated/galvanized and thus dangerous to weld. If it's kind of a gritty/greasy texture it's usually clean, weldable steel(just make sure the magnet sticks as well so you know it's some kind of steel).
Post a pic and we can probably tell you. Or if you really don't feel confident ID'ing it, just weld it outside with a fan blowing, that should keep the fumes away from you if there are any.

 

[ezcome-ezgo]

If it passes the"silver colored zinc coating" test, hit an inconspicuous area with a grinder and see if it throws sparks.

 

[itsid]

I think most galvanisation isn't especially healthy when welding, is it..
I mean phosphorised (mostly yellow) doesn't sound too pleasing ...

I'd grind off all coating before welding anyways, just to ease the ventilation task a bit either way.
since you want a good clean surface anyways.

If one can or cannot weld it then pretty much is solely dependend on the weld settings and filler material (if any)
as far as the pros on yt say at least..
if _I_ can weld it or not is on a different page though.. (if it's not easy to weld the answer for me would be "No" most of the time I guess )
I don't think I can make such judgement for anyone else though

So yeah.. clean it up as good as you can (remove coatings when in doubt) and give it a test.

'sid