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galvanising chassis?
JIMMY MAC - 21/6/14 at 06:11 PM

Hi to all,

This is my first post on the site and ill be here for a long time to come BY THE LOOKS OF IT .

I've bought a chassis and its maker is unknown I think it could be a tiger avon but I don't know no chassis numbers etc
so ill take it for being anything

I stripped it down and was wondering if anyone has had their chassis galvanised possibly the wish bones aswell

I've not seen any done and wondered if there was a reason they aren't done or I'm I just not looking hard enough

any help or info would be grateful


car itself has a rover k series caterham bell housing ford box sierra diff Cortina hubs

id like to td or mx5 but dunno I'll see what develops threw the build

I don't know how to put pics up any help there to plz

Jmac

mark chandler - 21/6/14 at 06:21 PM

I would be concerned about having the chassis dipped, if they get it a bit hot then it may not come back straight, a decent rub down and paint is all that is really required.

[Edited on 21/6/14 by mark chandler]

coozer - 21/6/14 at 07:48 PM

Galvanising is very hot so it can warp the chassis and it is thick so will make the it very heavy.

Take it along to your local offshore place and get it painted with what they use on oil rigs.

pjay - 21/6/14 at 09:15 PM

I looked at this option and from what I could gather a galvanised chassis is more difficult to weld and therefore repair etc.

Kdempsie - 21/6/14 at 10:10 PM

It's quite difficult to galvanise a frame that wasn't manufactured with that in mind. There needs to be a path all the way though the frame sections so that air is not trapped, that can cause the box sections to essentially explode when in the zinc bath, generally that means an internal hole drilled at every joint and open ends. Galvanisers are very careful about this. The other issues about frame distortion would also put me in the direction of powder coat or painting.

Keith.

Irony - 21/6/14 at 11:04 PM

quote:
Originally posted by coozer
Galvanising is very hot so it can warp the chassis and it is thick so will make the it very heavy.Flesh, e it along to your local offshore plaMighd get it painted with what they use on oil rigs.


I have some jotamastic 87 from Shepard marine. I think it has a 10 year submerged in salt water guarantee. Couple that with their Hardtop Flexi. That's what jcbs are planted with.

scott h - 21/6/14 at 11:13 PM

I am currently restoring a Marlin Berlinetta and I got the chassis galvanized a couple of months ago. There needs to be holes drilled to let the hot air out or it could explode and also let the solution in. From memory it reaches 450 c. There were a couple of flat sheet parts that did slightly wrinkle but other than that it was a good job. I did however get it painted aswell because after looking at the silver chassis for a few weeks I decided it should be black.

The most important thing is getting the holes drilled in the correct positions, if you are not sure you should get someone with experience of galvanizing to keep you right. When I took my chassis in they asked for permission to drill more holes if required, if you refuse and more holes are required they will not galvanize it and you may be charged, in the event they did drill a couple more. I am pleased with the result and would do it again because it is the ultimate in rust protection.

My chassis was sand blasted and galvanized by Scottish Galvanizers in Glasgow. It took a week and cost £260 all in. I later painted it with etch primer then top coat which was not originally planned.

James - 22/6/14 at 08:17 AM

I've not found a spot of rust on my chassis and it passed SVA 8 years ago with the chassis painted some time before that.

This was with a couple of tins of Screwfix Red Oxide followed by several coats of Homebase Exterior Black Gloss so cost about £20.

At this rate I suspect the chassis will out last me!

Cheers,
James

JIMMY MAC - 22/6/14 at 03:56 PM

Hi all,

thanks for your thoughts/reply's

distortion was the worry or bad handling cut from a height and left to fall while still hot would just take a new shape .

Well the red oxide certainly is not to be sniffed at for £20 and if it lasts 8 year then ill have some of that and if some mods are needed then its easily repaired. I thought dipped then forgotten about but for that kinda price then Im easily swayed

cheers all

43655 - 22/6/14 at 03:58 PM

doesn't powdercoating bake at ~400 degrees C anyway?
Neither should be enough to affect the chassis; i'm no metallurgist but eat treatment such as tempering happens a lot higher and would only affect it if there were stresses built into the chassis.

Could be a nice idea for suspension components which shouldn't be thickly painted.

How does it compare to zinc passivating?

brum_gustavo - 22/6/14 at 08:13 PM

The locost chassis is well braced, if it were to distort it would do so from tensions arising from welding alone. Venting holes would be, in my opinion, the main concern. Every tube that is not open to the atmosphere should be drilled in a way that allows for draining and venting (this is more critical in hot-dip galvanizing). Although powdercoating is much simpler and just as efficient, plus you don´t need to paint it and it looks better. IMHO
I´ve painted mine in enamel and applied a rubber coating underneath the cockpit floors.

mcerd1 - 23/6/14 at 08:06 AM

quote:
Originally posted by 43655
doesn't powdercoating bake at ~400 degrees C anyway?
Neither should be enough to affect the chassis; i'm no metallurgist but eat treatment such as tempering happens a lot higher and would only affect it if there were stresses built into the chassis.

Could be a nice idea for suspension components which shouldn't be thickly painted.

How does it compare to zinc passivating?


I thought powder coating was only 200°C ??

passivating is something you do to zinc afterwards to give it a little extra protection or change the colour - its normally done to zinc plated materials (aka: electrogalvanized)
zinc plating is often only ~5µm thick, but hot dip galvanizing is about 85µm thick - so 17times better
but that thicker than most paint !


Hot dip galv. requires the parts to be dipped into molten zinc long enough for them to heat up to the same temperature as the molten zinc (at least 460°C)


more than enough heat to give you some bad distortions (we get much bigger/heavier steel distorted in the galv bath at my work)


that's after its been cleaned off by getting dipped in caustic and then acid solutions

as above if large enough vent holes aren't carefully added to every possible nook and cranny then you will get one or more of the following results:

1 - zinc gets stuck inside one or more tubes = really heavy bits in your chassis (and the galvanizer will charge you for the extra zinc used) - this happened to a dax cobra chassis I know of - it ended up 40kg heavier on one side than the other

2 - a tube has no vent holes and a tiny bit of moisture inside from the day it was welded = the tube explodes in the galv. bath (I've seen the results of this first hand) sometimes it doesn't burst and just puffs out like a puffer fish

3 - some acid gets suck in a little crack or a bad weld = this leaks back out afterwards and strips of some of the galv. - if it you get a bad case of this you might as well have never galvanized it (acid is great at removing zinc)



and the space frame chassis are so complex that by the time you had enough holes in it would be like Swiss cheese...

[Edited on 23/6/2014 by mcerd1]

TimC - 23/6/14 at 11:46 AM

I can't comment through experience but do know that Autotune quite frequently galvanise Gemini chassis - which is just ERW 1" tube.

alfas - 24/6/14 at 10:41 PM

if the chassis tubes are drilled in specific places with small holes air can escape, as well as the excess zinc.

it wont warp as the chassis is tough enough.

lots of TVR chassis have been galvanized during restoration without problem...and from my personal expirience:

i owned a autotune gemini where the builder decided to galvanize the chassis.. (gemini´s have also a spaceframe square tube chassis like a seven)...and it was spot on...geometric and corrosion wise.

for me galvanizing is the one and only anticorrosive coating which works!!

JIMMY MAC - 25/6/14 at 06:14 PM

Thanks all for your input cheers guys

it will certainly be just a few coats of paint as the price will be right
Then if any mods upgrade need doing it's an easy repair

mcerd1 - 26/6/14 at 08:09 AM

have you looked at the POR15 paints ?

they aren't cheap, but they get a very good name for protecting chassis