best way to weld/repair rear arch?

[yayoboy]

as title, this is what i have to repair,

ive cut the most of it out, im waiting for my air saw to arrive and then ill cut the rest out, the question im asking really apart from the obvious of making a plate to suit the hole ive cut, is how to protect the plate im welding in from rusting, ie do i zinc primer the front and back of it then weld it on? any ideas welcome thanks, sean

 

[Timo_k]

Hi, I usually make the plate first then I know exactly where to cut / grind. You could use some sort of weld through primer on the back of the plate,but it woud probably still burn off if you seam welded. You could try and spray waxoyl or something into the cavity after you have welded the new metal in to give it more protection. you may have to drill a hole for this then stick a grommet in it after.

I often use galvanised sheet to make repair plates because i get off cuts of it for free but you have to grind the zinc coating off around the edge because it can give off nasty fumes when welded. The zinc primer might give off these fumes as well when welded I think its cyanide or arsenic or maybe a bit off both but as long as you work in a ventilated area it should be ok.

 

[Bsmith]

I would weld the plate in as bare metal, blast some waxoil or similar in from the hole further back or drill a hole in the new plate so it can be done, paint the outer side, plug the hole.

 

[Blackjack]

When I used to do a lot of that, if it was a closed section or difficult to get at, I used to degrease the plate, scuff the back of it up, and aerosol primer it.

OK, you burn off the primer where it's welded, but that still leaves most of it covered and if you can't see it, you don't know if it's waxoyled or whatever.

 

[steveo3002]

weld thru primer seems to stay on ...obviously the edges will burn

main thing is drill a couple of holes and get some cavity wax in there while its still fresh