Galvanising bits - info and opinions, please

Post by **HarryMann** » 14 Mar 2007, 13:20

Good point about the thread holes... suppose all depends on original thread tolerances and thickness of galv. I wouldn't have thought at SDP that body was given a partic. thick coating.

Post by **crazydiamond** » 14 Mar 2007, 14:09

Another big problem with hot galvanising is that you have to be very careful how you dip to prevent gas build up in box sections, they must have a way out for gasses etc whilst dipping otherwise i've been told things sort of blow up and cause splashing of hot zinc, something to avoid. other thought is distortion of large flat body panels, this will happen if you heat one part first then the rest. sometimes components need to be pre-heated before platting. Lots of problems, when a really good coating of Waxoil in all the hollow sections and underside will do a pretty good job anyway. My van was waxoiled from new and it still is intact on most areas.

Post by **Mudlark** » 15 Mar 2007, 00:07

Had two new large hot galvanised steel gates fitted to our yard 18 months ago and what do you know there's rust in them already. If you want a job doing and all that .......

Post by **airhead** » 15 Mar 2007, 01:37

I had a small patch of bare metal on my tailgate right up until I got the van resprayed. It never even turned brown with rust! It was always silver, which would tell me that the steel used then was very good. It lasted like that for over a year, in all sorts of weather. Either that or mine is gavanised!

Eh no. Not likely really.

Post by **Russel** » 15 Mar 2007, 06:58

The T3 in question was totaly galvinized as a body shell.The original owner who had this done worked for VW.I know the last owner who sold it at vanfest.He is a very knowlegable vw inthusiast and trader.(works on and converts them)
Audi galvanise some of their range of vehicles.
There are other problems related to galvanising.If u have an accident this will crack the galvanising(where bending of the metal takes place)and doing body work over galvanised metal is a pain in the ar....
The other thing is u would have to have a brand new body shell to start with.

Post by **mister smith** » 15 Mar 2007, 10:22

about blocked off thread holes, surely you put grease on yer nuts

yeah, there's no arguing it's a quick and simple job. Either the coating would have to be thin, and a tap / thread cleaner run through all captive nuts etc, or as you say blocked off. Nothing's ever perfect...

harrymann,

I'm honestly not sure how they control the thickness, but I know they can.

Could be different solutions, different prepping or simply just time spent in the tank.

@ crazydiamond,

thats right about closed box sections. The galv operator wouldn't dip something they thought had any closed sections. If they think something is closed. they drill holes in it, plain and simple. Hot galv needs to be able to run in at the top of a section, and out at the bottom

I doubt though that there is a sealed section anywhere on any pressed steel built vehicles.

I know waxoyl is a good bet, but it will still get washed away, imagine the confidence you would have in a van that had been galved, waxoyled & undersealed.

@Mudlark

10 to 1 that the bit that's rusting is where they changed/welded a bit AFTER galvanizing, then sprayed it with a bit of 'Galvafroid' (zinc paint, not quite the same as a hot dip)

@russel,

good info there,

I know welding 'galv' is a nightmare (not to mention the lack of galv after welding).

1 question though, why do you say you would need a brand new body shell?

You know 'old school' fabricators will always stand something to be galved outside for a week or two, to let rust start. This allegedly helps the zinc key to it properly...

It's good at least to know somebody has done it. I may be mad, but at least now I know i'm not alone

Post by **Russel** » 15 Mar 2007, 19:36

Because it would be imposible to find a dent and rust free body to galvasize at their age.
Doing body work on top of galvanising is a pain in the ar...
To prep the body u would have to remove all sealants and ruberisers of ure shell.And vw love very thick and difficult to remove ruberiser underneath.
Or at imense cost find someone with a very dig acid bath (with very strong acid)

Post by **HarryMann** » 16 Mar 2007, 02:49

Hot dip galvanising involves alakaline cleaning first and then acid pickling to remove scale and rust, as well as a pre-flux dip treatment, a bit like soldering flux. Then the bond is a strong and fairly immediate chemical bond provided the material is clean - perfectly clean. The rustier the part,a nd the more surface scale, the longer the acid dip.

The fumes from almost any form of welding through zinc are dangerous...