-
As @Constable_Savage said, likely just very cheap steel. It depends what you want to make if you can get enough length (fnar). And as with any salvaged stock, it the amount of extra prep required (in this case wire wheeling or grinding the rust/flaky paint off, cutting and straightening) versus just buying a few lengths new. Sometimes it works out, sometimes it doesn't. But it's good to recycle.
I'm still dining out on the kitchen worktop offcuts that @Dammit was offloading for my makery fuckery.
stevo_com-
Cheers - it's for a bike trailer (the frame thereof). The main square of one of those signs looks like it could serve as a passable base, with enough additional material to get four uprights of about 18" each. My understanding is that if stick welding, you don't need to get the metal that clean, but I'm a total novice.
fizzy.bleach
These temporary road sign frames:
Are they made of anything more complicated/toxic than mild steel? I need some angle iron for welding and there's loads near me just dumped.