Drilling Galv Metal - How best to protect?

[manic]

Unfortunately it looks like I must drill a couple of holes in my galvanised bulkhead if I want to install Air Con. I really do not like the idea of breaking my zinc barrier so I am hoping there is something as robust that I can apply to protect the exposed metal? The area around the mount will get wet and any protection applied to the drilled holes will need to withstand the grate of the mounting bolts.

Zinc rich paint the best option?

[101RRS]

Cold Gal on the exposed metal and covering across to the galvanising to make a seamless coat.

Garry

[isuzurover]

... breaking my zinc barrier ...

This seems to suggest a misunderstanding. The zinc is a sacraficial coating, not a barrier. So drilling or scratching through the zinc coating will not decrease the protection of the steel. You can remove the zinc up to ~8 mm diameter and the bare steel underneath will still be protected from corrosion by the surrounding zinc.

But if it makes you feel better - buy some cold gal - but make sure you get the good stuff (>>97% zinc).

[Blknight.aus]

yep, cold gal it, but depending on what bulkhead you have you might be able to route the AC through some pre-exisintg plates/blankers that are in situe for left/right hand drive versions.

[manic]

This seems to suggest a misunderstanding. The zinc is a sacraficial coating, not a barrier. So drilling or scratching through the zinc coating will not decrease the protection of the steel. You can remove the zinc up to ~8 mm diameter and the bare steel underneath will still be protected from corrosion by the surrounding zinc.

But if it makes you feel better - buy some cold gal - but make sure you get the good stuff (>>97% zinc).

Yes of course, barrier not entirely correct but it helped describe my concerns. I didn't think that a drilled hole with exposed metal would be protected by the surrounding zinc. This makes me feel much better! I was told not to drill a chassis/bulkhead after its been galvanised.


So for added peace of mind where do I get the good stuff with 97% zinc?

[Blknight.aus]

bunnings will have it but you have to look at the cans for the content, they are usually the priciest can.

[V8Ian]

Any industrial supply shop will have quality cold gal in pressure packs.

[isuzurover]

...

So for added peace of mind where do I get the good stuff with 97% zinc?

As above, but IME the stuff in tins has the highest zinc content. I used to have a 1L tin of cold gal that had the consistency of mud. I think it was >99% zinc.

[jimr1]

lAs the old roosters have said , cold gal . Also think about putting rubber gromits in the drilled holes , before air con pipes .regards jimr1...

[Xtreme]

Also, take care to clean up the swarf after drilling as this rusts very quickly and will eat into whatever it has settled on.