Welding without disturbing paint

[BrokenBiker]

When I have got my hands on another mig the first job I have to tackle is the rust on the inner skin of the bonnet on the Alfa. It's quite bad, I fact every time I close the bonnet it showers the floor with quite sizeable chunks of rust. It's not an mot issue but it's annoying me.

Problem, the inner skin is obviously welded directly to the outer skin and the outer skin has immaculate paint on it, it's the only panel on the car that I am happy with the paint and although I want to have he car respected I don't want to do it any time soon so want to try and weld the bonnet rust without burning the paint off the outer skin

Any ideas or am I being far too optimistic and should I just buy a tin of paint in advance?

My only real idea is to put a large soaking wet rag on top the areas to be welded and then tack and allow to fully cool the. Tack again and fully cool etc, but that will take days with the amount of welding that's needed

 

[Justme]

Cant see it working.

Can you bond it instead?

 

[rikrobson]

bonnets are usually a single skin, backed with an open framework. is it the inside of the outer or the franework that is rusty? Pictures may help

 

[BrokenBiker]

I'm ta a spot welded panel originally I think but I want to weld it on with the original weld points but also weld up a few lips that are trapping moisture to try and stop it rusting so much in the future

 

[steveo3002]

pictures would help

ive welded a part of the inner frame on mine and it didnt mark the paint , i layed it on a soaked rag and went slow , that part wasnt in contact with the outer skin though

 

[normspanners]

If you are thinking of welding to one side of a 1mm piece of steel and not disturb the paint on the other, there is no chance the weld penetration will be over 1mm, so good bye paint and goodbye surface, I would as said by ^Justme^ make a frame and bond it you can sand very gentle to key it,and will do the job lots of cars internal frames are bonded to door skins etc with lumps of resin type glue, or some use tigerbond as it is flexible.

 

[johnik]

most the bonnets i have seen are welded round the edge and just some sealant on the cross braces,if it wasnt originally like that i am sure that would be a better way to go.
you could make new sections for the braces,weld them to the existing brace and bond the brace to bonnet panel ?.

 

[BrokenBiker]

My have to look into this a bit more then.

Bonding sounds easier and I could take the panel off, repair it away from the bonnet and ten bond it back on

 

[octo0072000]

Sickaflex tiger seal all PU type adhesive forget welding it or just get another bonnet

 

[BrokenBiker]

Might just get a bonnet to be honest, just had a good look and it's worse under the sound proofing.

 

[rikrobson]

I'd be looking at another bonnet to be honest. The tin worm os probably more invasine than you realise.

 

[500e]

http://www.shop3m.com/3m-automix-panel-bonding-adhesive-08115-200-ml-cartridge.html

 

[BrokenBiker]

When I pulled the sound proofing down all the holes that hold the clips disintegrated... Have put it back on as best I can so will just look for a new bonnet in the right colour

 

[Rocketman]

Another alfa bonnet in the right colour that hasn't started rusting. Could be a challenge finding one

 

[BrokenBiker]

Yep, may just leave it for now, prep the rest of the car for spraying the whole thing (few dents and needs a wing) and then weld Repair prices to the bonnet and have it all sprayed

 

[mike 109444]

If you think you are going to keep the ori bonnet then remove any loose rust and at least treat the rest to stop it progressing (get some phosphoric acid and a big brush)

 

[500e]

It's an Alfa where are you going to find a non rusty bonnet

 

[BrokenBiker]

Anyone know where the colour code is on an Alfa 147?

 

[500e]

 

[500e]

Usually on the bonnet or boot lid, occasionally on the top of LH strut mount a silver sticky thing