Galvanising of panels

[ST Man]

Hi to all

I was looking at the hinges on my bus which is a source of rust and started thinking. Why cant I take all my loose panels and galvanise them.
When I say loose panels I am thinking:
Front doors
Side doors
Rear Door
Engine lid
Safari window frames
Pop Out window frames
Front door window frames
Bumpers

After galvaninisig i will do normal paint etc. My thinking is that is will stop all the rust and protect the panls for many years to come. Most treatments cant get in the back/ under skins on doors but in a bath it will work great. Imaging some guy can do the whole bus.

So what do you guys think?

Leon

[Retro13]

A friend of mine operates a small zinc plating plant from home; as a result I make extensive use of his services in my bike restorations, as well as my current Kestrel buggy rebuild. What we've found to be very succesful is when we plate the saddle pans on the bikes before painting and then upholstering them. This gives very good protection against corrosion, as the foam in the saddles tends to trap moisture.

However, electrodepostion galvanisation (it's proper name) doesn't work when it comes to plating the inside of components, as there isn't enough 'throw' from the anode for the material to flow into the crevices of the job (cathode). Instead, it 'sticks' to the nearest surface. This can be overcome by placing an anode inside the job (part), but this is impractical and often not possible. Another factor to consider is the size of the part, which is restricted by the size of the bath.

A more common way of galvanising items is to have them hot-dip galvanised, whereby the job is submerged in a bath of molten zinc. Corrugated roof sheeting is normally treated this way. This is probably a better way of doing it, although I don't know of any places off the top of my head that do this.

What I've found from experience though is, just like painting, the finish is entirely dependent on the prep work. So if the part is very corroded, it will come out rough unless it is smoothed off first. A lot of guys have had varying degrees of success of rust removal by using reverse electrolosys, which is when the polarity is reversed in the electroplating process and the job becomes the anode. The corrosion is then drawn away from the job onto the cathode. The guys usually do it to de-rust an old fuel tank and it's a messy and time consuming job, but if you get it right it works brilliantly.

I hope this helps...

[ST Man]

Thank you REtro helps alot

[Retro13]

Only a pleasure. Hope you come right with your project; the Samba looks well wicked!

[Golfmad]

How does the galvanising affect painting - I heard that automotive paint struggles to stick to gavanised metal?

[Barry]

Anything will stick with the right primer. (on edit: and preparation. Thanks for pointing out about the wax Herman - cleaning anything properly before paint is crucial)

Not sure what your panels are going to look like after hot dip galvanising though..........

Electrolytic rust removal (google it) works great, but it is also line of sight, so getting inside panels is tough. Molasses, vinegar etc will also all work. I would go for a simple phosphoric acid based metal prep, neutralised with (a LITTLE) bicarb in the rinse water, and then hit it with a GOOD marine type epoxy primer. Guarantee you won't have issues in your lifetime if done right.

[Retro13]

I agree with Barry. The phosphoric acid prep and neutralizing is a better, simpler (and cheaper) way to go.
Hot-dip galvanising is an industrial process which could leave your parts looking a bit questionable.

I've also been experimenting with a product called Deoxidine, which converts the rust, neutralises the metal and forms a base for paint. It's designed to be used in a dipping application. Will try give feedback when I start posting my rebuild progress.
As always, prep is the most important element to any successful finish.

[retrovan]

Please note that with Hot Dip galvanizing, the part must be strong to resist distortion.
You can hot dip battery boxes, pedals shafts and such like, but if you put in a door, it will distort to the extent of having to be scraped, you will never get it strait.
When VW did galvanized body parts in the past as well as now, the plated are per-galvanized so they can be stretched back to strait in the presses.

What you can do, is find a place that does "E-Coating" this is an electrostatic dip process that will flow in just about every where, and is then baked.
All new car are done this way.(this gives the black colour on the parts.

If you look at my Fastback thread, you will see that I have done this with all my lose panels. http://www.aircooledvwsa.co.za/viewtopi ... 30#p196663

When you do Galvanize anything, do remember that all hot dip guys have WAX on their hot dip tanks, this protects the parts if not properly coated, and keeps the heat into the tank. So before you do anything, you need to remove this, as if you do not, your paint will not stick, best give it a light sand blast before painting and also a good thinners wipe. that is why you always see paint peel off galv.

Hope this helps

Herman

[ST Man]

Glad I asked learining a lot thanx all

[hendriks]

hi St Man,

I used to Work for the Hot Dip Galvanizer Assositon of SA. (http://www.hdgasa.co.za )

Most of what the other guys have said is correct.

in a nutshell:

0.02 - 3.9mm steel is normally pre-galvanized - this is a process where steel "drawn through" molten Zinc continually and then coiled. the martial is then unrolled again in flat sheets of metal that can then be shaped and formed: IBR, corrugated iron and light steel structure buildings, the steel sections used for dry walling and so on.
the reason the steel can be bent and shaped is because the Zinc coating is very thin and does not easily crack.

4mm and up - the steel is to thick to be coiled and shaped and is therefor used to fabricate into what ever structure and then sent for hot Dip Galvanizing.
as Retrovan mentioned, larger structures (especially with thinner steel sections) need additional strengthening in order to avoid distortion.

the reason a Land rover chassis are often Galvanized is because it is heavy steel. if you were to ?hot dip Galvanize a vehicle body, you are guaranteed to have zinc in every crevice and corner, but because of the large thin sections welded to the thicker pillars and chassis the distortion will be very bad. - i can show you many reports of structures that distort because of this design problem.

the process;
- take steel that has been cleaned (hidrochlaric acid, sand blasting)
- dip it in molten zinc (450 degree Celsius) for a few seconds and allow the metallurgical reaction to take place
- remove from the zinc and either - air cool
- quench in a passivization bath (an oily residue is left on the surface to protect against flash corrosion)

when you want to paint over Hot dip galvanizing (this is called a duplex coating) the passivization layer needs to be removed - (zinc iron cleaner - can get it f builders ware house/paint shop. sweep blasting (same a sand blasting, just at a much lower blasting temp with smaller grid).
a zinc compatible undercoat must be used and then the top coat or 2 or 3 - depending on the application.


The alternative is to fabricate your panes from pre galvanized sheet metal and weld it in place. obviously where you weld the zinc will burn off and you will not be able to protect it on the inside again. the outside can be coated with a zinc rich paint.

zinc protects carbon steel by slowly "sacrificial" itself. in other words if you cut a piece of corrugated iron, only the edge will show rust, but the rust will not "run". we have all seen on our VW's how the paint starts to "bubble" and if you scrape that off there is some nice rust???

because galvanizing is a metallurgical reaction and not just applied on top of the steel "under corrosion creep" is not possible.

anyway - enough of the Galvanizing lesson. I can give you all the information you could ever need form designing an item - all the way to repairing Hot Dip Galvanized items years after it was first coated.

moisture is the biggest contributor to metal rusting, so if you can prevent moisture from getting to the inside channels/ pillars, rust wont bother you. painting a panel before welding it seems pointless, but at least some of the inside panel will be protected and this will already help.

no matter what rust prevention you decide to go with: hot dip galvanizing, painting. electro-galvanizing, plating, electro-painting and and and....
PREPARATION IS THE KEY TO LONG LASTING CORROSION PROTECTION

Smaller components as Retrovan mentioned can easily be hot dip galvanized and will ensure long lasting protection.

i know i went on a bit.....