Thread: Duragal

Originally Posted by DoctorWu

How reliable, rust resistant that is, are welded and properly painted Duragal joints? haven't decided on material yet but most likely 2mm walled RHS.

Can't say that Duragal has much to do with the rust-resistance of the weld area - it's just molten steel, all the zinc gets burnt up during the weld.

That said, I've found the "structural silver" spray that's designed to match Duragal is very thin and needs a few coats before it becomes water tight. The better option is to spray first with cold gal, which seems to be a bit thicker, then overspray with structural silver.

I have mentioned before in another thread about the effect of galvanising and its ability to keep rust away from a weld.
When GMH first released the HQ onto the market they were critisised for punching holes in sheet galvanised steel for the bonnet brackets and not coating the edges of the sheet. In retaliation tests were conducted with gal sheet with different sized holes punched in it and see how that affected the surrounding area when subjected to a rusty environment. The results wer that a hole of about 50mm could be exposed to to a rusty environment with NO rust forming. The galvanising sets up an electrolytic action which in effect is atiny electrical current that keeps rust away
My front gate is a great example. It is 25mm gal pipe (OK its not Duragal) and where I have welded it together, I never used any paint over the welds. Result after 30 years....the welds have turned a black/dark brown colour and on inspection no rust on the surface
So I think that, as Rusty Arc has said, for looks a squirt of pressure pack silver would keep the Duragal integrity intact. The only draw back with the stuff is that it doesn't last forever and will need fresh paint over the years

My experience, however, is that joins in Duragal with a just quick squirt of structural silver over the top soon have rust marks leaching through the paint.

It may be only surface rust, not structural, but it looks bad. That's why I recommend a good coat of cold gal followed by silver over the top.

Thanks for the comments. I was thinking out aloud because the last time I had material galvanised it took me about 2 days to clean up all the blobs and dags and pits in preparation for painting so I don't want to go through that again. I always flapdisc joints before welding duragal but mostly never bothered about the internal bits. This time I'll do what someone else suggested and dip joint ends a few mm's into a 10% diluted hydrochloric and totally minimise the possibility of fumes. Yes, the zinc does it's job