Years ago I pulled a piece of 2", 2mm wall box section out of a skip. At the time I thought it was aluminium as it had a bit of a white dusty-ness to it.

I've recently cut some bits off to make brackets for my brake lines. I realised then that it's not actually box section, it's been folded into a box shape but with a gap on one side where it doesn't fully meet.

It's very hard, drilling it has been tougher than mild steel. So i'm fairly sure it's not alu!

It's never discoloured since i've had it, and even the parts i've cut up in the last few weeks haven't started to rust at all on the cut edges.

There are some pictures of the brackets on my blog here: https://meandthekitcar.wordpress.com/2020/10/30/brakes-8-2/

I'm wondering if it's galvanised stainless, in which case - what should I do to paint it effectively?

Hard to tell what it is, but you don't get galvanised stainless.

Does a magnet stick to it?

If its light its aluminium if its heavy its stainless, if its very heavy its probably radioactive.

I say that slightly in jest as I have worked with oil well logging tools made from both stainless and titanium uranium alloys in the past. These are more common metals than you might think, and yes they too sometimes ended up in a skip. It pays to be a bit careful with stuff you find in skips.

Why are you painting it anyway?

It’s hard to tell butto me it looks like it could be galvatite.

Zintec or Galvanised Steel?

As said above is it magnetic?

Looks like Galvanised Steel to me - nothing exotic

Galvanised steel.. To stop rust on cut surfaces you need a cold galvanising spray. Or acid etch primer then normal paint. Normal primers will not stick to zinc coating unless weathered...

[Edited on 12/11/20 by Bluemoon]

I'd go with galvanised steel (there's many grades of steel) or stainless steel. If there's no rust at all and it's very hard I'd edge toward stainless steel. You can try the magnet test, but there are magnetic and non-magnetic stainless steels so that may be inconclusive.

If there's no rust or corrosion do you really need to paint it?

When building my MK Indy I fabricated some brackets from Aluminium alloy and didn't bother painting them. Rivetted the bracket to the chassis and fixed the part to the bracket in a suitable way, job done.

Sorry - didn't look at your picture before!

I'd say galvanised steel, cheap as chips and probably why it ended up in a skip. I'd say the parts were cut, bent and then galvanised hence no corrosion on the edges. If you since cut the parts and drilled holes the that opens up the galvanising t allow corrosion in. In which case I'd follow Bluemoon's advice on coating the parts to prevent corrosion setting in.

There's good reasons galvanised field gates aren't painted. Extra cost to paint them 'cos they won't take cheap paint and the galvanising is there to stop the corrosion anyway.

Thanks guys. No idea why I didn't think to pop a magnet on it. It's magnetic (so steel unless there's something else i've missed!).

I'll etch prime then topcoat just to be on the safe side. Don't want to find rust developing down the line, once they're bonded in place...

Just weld it and you'll find if it's galvanized
Hands up who's given themselves zinc fume poisoning (me!)

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Hands up who's given themselves zinc fume poisoning (me!)

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i love it when the doc does something silly - makes me feel a bit better when i've "made a mistake"