Lotus Elan

Chassis paint or not to paint

PostPost by: ken_apple » Fri Nov 04, 2016 1:15 pm

I am looking for some advise on whether to paint a galvanises chassis or not.

I am doing a complete rebuild of 1971 +2s the car has had a previous restoration which included a new Lotus galvanised chassis, which is in great shape. No evidence of any damage to the galvanising and no rust.

As I have the opportunity to paint it now with a suitable epoxy primer that can be pained over galvanising, should I take it?
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PostPost by: nmauduit » Fri Nov 04, 2016 1:59 pm

a difficulty of painting galvanized steel comes from the time elapsed since the galvanization :

http://www.galvanizeit.org/images/uploa ... tsteel.pdf

within the appropriate window (i.e. after 1 year of maturation...) , I like to apply polyurethane paint (rather than hard baked epoxy) for its flexibility on the chassis under use - and to look original looking underneath.
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PostPost by: nigelrbfurness » Sat Nov 05, 2016 9:32 am

From a practical perspective, I find a painted chassis easier to keep clean and it looks better and more cared-for too. I found that red garage door paint works very well directly on aged galvanising and is very long lasting - my current chassis sows no signs of peeling after ten years or so. It also seems quite chip resistant.

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PostPost by: worzel » Sat Nov 05, 2016 12:01 pm

Hi

To ensure adhesion to galvanised metal you need to first apply something called Mordant Wash (don't ask why it's so named I've no idea).

Immediately this is applied the grey galvanised surface turns very dark and is ready for any topcoat once dried. I used it years ago on a galvanised frame for a Scimitar.

Regards


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PostPost by: elanfan1 » Sat Nov 05, 2016 12:11 pm

https://en.m.wikipedia.org/wiki/Mordant

Not sure that clarifies anything.

I'd have thought an etch primer would do the job. IMHO paint it, looks original and much smarter.
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PostPost by: Grizzly » Sat Nov 05, 2016 1:15 pm

As above, be careful if you paint it the top surface of the Galv sort of oxidises and once that happens not much will stick properly to it.
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PostPost by: Elanintheforest » Sat Nov 05, 2016 2:47 pm

Grizzly wrote:As above, be careful if you paint it the top surface of the Galv sort of oxidises and once that happens not much will stick properly to it.

Is that what happens?! I have an Aussie Mini Moke with a galvanised bodyshell, and that has to be painted every few years as paint just won't stick!

Agree with the above to get the chassis painted. It doesn't look good under the bonnet with a bare chassis, especially when it starts to get a bit powdery!!
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PostPost by: StressCraxx » Sun Nov 06, 2016 2:33 am

Galvanized steel can be painted with the correct preparation. Porsche galvanizes their entire bodies prior to welding them together.

I used 220 grit paper then muratic acid to etch the zinc surface. I rinsed the muratic acid with water, then neutralized with baking soda then rinsed again.

Primer was a standard automotive primer for epoxy. The paint I used was DuPont Nason with a hardener that was applied with a HVLP sprayer.

Below is a link to surface prep of galvanized steel from an industry group.

http://www.galvanizeit.org/specification-and-inspection/specifying-duplex-systems/preparing-hdg-for-paint
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PostPost by: Sea Ranch » Sun Nov 06, 2016 6:31 am

nmauduit wrote:a difficulty of painting galvanized steel comes from the time elapsed since the galvanization :

http://www.galvanizeit.org/images/uploa ... tsteel.pdf

within the appropriate window (i.e. after 1 year of maturation...) , I like to apply polyurethane paint (rather than hard baked epoxy) for its flexibility on the chassis under use - and to look original looking underneath.


Just to add another view . . .

If you read the pdf linked above, you'll see that fresh out of the "zinc kettle" or after one year's time, a hot-dipped galvanized surface will take paint without problems:

The adhesion of paint onto galvanized steel becomes a very small problem when the galvanized coating has weathered for at least a one-year period. The zinc corrosion products form a very dense, insoluble protective layer that accepts a paint coat readily. A brand new galvanized coating also experiences few adhesion problems within the first 24 to 48 hours after coating.

This from a very careful study of the issue.

I would paint it (and black, as the factory did use the so-called red oxide primer on Plus 2 original chassis' but then top-coated them with black).

Regards,

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PostPost by: ken_apple » Sun Nov 06, 2016 7:26 am

Thank you for all the comments, It seems the consensus is that a painted chassis would look best and is more factory correct, but there are the problems with painting galvanised steel.

In the marine industry we frequently paint galvanised steel structure, typically the surface preparation and painting conditions are far from ideal. The product that I have used before is Jotun Jotamastic 90.

http://www.jotun.com/Datasheets/Download?url=%2FTDS%2FTDS__16560__Jotamastic+90__Euk__GB.pdf

I haven't come across adhesion problems with this product before so was planning on using it on the chassis.
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PostPost by: Grizzly » Sun Nov 06, 2016 11:07 am

ken_apple wrote:In the marine industry we frequently paint galvanised steel structure, typically the surface preparation and painting conditions are far from ideal. The product that I have used before is Jotun Jotamastic 90.

We have used that in the past for chassis and your right 2 pack Epoxy sticks better than etch etc but i'd still be weary putting it over old Galv without some serious prep work first.... In my line of work it's hard to comment on longevity, but with that said i only use epoxy Powder coat for chassis / chassis components which usually is indestructible, but i've seen it stone chip off an 80's Lotus Galv chassis and from memory they prep'd that by shot blasting it on a wide fan.

I'm not saying painting over old Galv can't be done but even Epoxy has a hard time keying to it if it's old. It's worth looking into it well because if you have it all back together and it starts coming off it will look worse than if you had left it.
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PostPost by: alan.barker » Mon Nov 07, 2016 7:07 am

Ken,
if it's galvanised it has already the best protection and doesn't need painting.
On my 1972 Elan Sprint it has a Lotus galvanised chassis not painted and still looks very nice since the day it was fitted many years ago by Miles Wilkins
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PostPost by: Grizzly » Mon Nov 07, 2016 11:22 am

It's a personal preference thing, Galv is very good but is still corrodes just at a much slower rate (it's a sacrificial coating) so if you only use your car during the summer and it never gets to see anything like Salt off the road etc they i'm sure it will stay looking good for a long time, but with that said i know people that have Landrovers just for use in Winter and they don't look so nice.
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PostPost by: gus » Mon Nov 07, 2016 11:45 am

In the early 80's I had a new pickup truck with a galvy bed that was painted, paint flew off wherever touched.

Newer trucks seem to have figured it out

quick scan of the internet says 'surface prep'

I would paint as I think it looks more original
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PostPost by: alan.barker » Mon Nov 07, 2016 12:57 pm

Grizzly,
my 1972 Lotus Elan Sprint fhc has been sacrificing it's galvanised chassis for the last 30+ years and it is still galvanised :roll: :roll: :roll:
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