I have bought a damaged Volvo V40. For the repairs, I had to cut out some spot welds. The chassis is fully galvanised.

I have tried to plug weld the removed spot welds, but without success. I expect the zinc to be the problem. Due to limited access I have cleaned the area with a screw driver. Anyone some tips & tricks??

[Edited on 19/2/10 by maartenromijn]

What about brazing with a gas and brazing rods.

Lol... I read the title all wrong - thought it was "how to SPOT REPAIR welds on galvanised chassis"!

Get one of them flap wheel sanding discs and clean the area of all the zinc coating before trying to weld.

Also clean a patch for your earth electrode too.

Try not to breathe in the zinc dust when sanding and if any white zinc oxide residue appears when welding you need to sand it more / a wider area around the intended weld.

Geoff

You need to clean the zinc off to weld or braze, and don't breeth the fumes.....

quote:

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Originally posted by r1_pete
You need to clean the zinc off to weld or braze, and don't breeth the fumes.....

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get some hydrochloric acid in there, that should do the trick!

Local steel fabricators told me to be really careful with ventilation when welding galvanised metal. The fumes are very nasty/carcinogenic.

If there isn't room for mr angry then a powerfile would be the best option.
You need to clear far enough that the galv doesn't vaporise in the heat of the weld.

Don't know if the fumes are carcinogenic or not, but they will certainly give you flu symptoms if you breath any.

Spray with weld through primer before welding and it should help prevent the tin worm in the future.

Weld thru primer == zinc rich paint....
You can arc/mag (MAG - argon CO2 mix, slightly higher wire feed/current that's all) weld zinc coated steel, but must take serious precautions with ventilation.

Can you reach with Oxy Acetylene welding torch?
Play around your weld area just make sure you donīt breath the fumes.
No permanent damage AFAIK but real nasty headaches.
My 2 pence...

You will not get metal fume fever from spot welding a few holes in a chassis in well ventilated conditions. It should weld with no problems and earth through it if it is still fairly clean but grinding it off is preferable.

use a dremmel or simmilar with a small grinding wheel

Well, I have used the angry grinder where possible, fake Dremel (rubbish) and sanding paper. Put up the current and wire speed a bit. Welds look very crappy, but seem to be holding.

I have no quick access to brazing and gas/oxy equipment.

Wleding fum es: its mell sa bit funyy, but I haev n ohean ac he hr

[Edited on 19/2/10 by maartenromijn]

no, seriously, 25% hydrochloric acid! It'll fizz through the zinc and leave te steel alone. Just wash it off afterwards.