[wojtech]

Can Mild steel or Stainless be used as a backing when building up Aluminium edges?
I have no copper to use and the thought of buying a large piece just for a quick project doesn't really interest me.

[nickn372]

I have done it. It works ok. You have to use a thick piece of steel and they will stick together a little bit where copper wouldn't do that but its not out of the question at all.

[wojtech]

I assume stainless will work better than mild?
Is there a risk of contaminating the welds? The piece is being used in a marine situation

[Otto Nobedder]

Stainless is the better choice, particularly in a marine application, as you're unlikely to contaminate a weld.

Brass works well, too.

Steve S

[fisher]

I have been using a big chunk of ally 40 x 40 mm, seems to work well, sometimes wrap some thin copper sheet being easier or cheaper to get, over it, haven't managedto weld to it yet..

[ajlskater1]

Becareful with brass it has since and out gasses, would not recommend it for backer over a gap. I have used it before and had that happen.