Welding Tips and Tricks

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.

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.

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

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

Brass works well, too.

Steve S

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..

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.