Powder Coating for Underbody

[142 Guy]

As I recall, TVRs have a tubular chassis with a FRP body attached to the chassis. TVR powder coated the chassis components and I do recall that chassis corrosion was one of the warnings on a used car check list. The inspection advice centered on the 'moisture trapped under the powder coat' problem indicating that the surface might look OK; but, death might lurk underneath.

I have powder coated pieces on my car. The first observation is that touch-up is not really possible unless you are just trying to color match with a conventional paint that uses an organic or water based carrier. The good / bad part of powder coating is that it allows the application of a much thicker and presumably more durable coat without sagging than you can get with more conventional liquid carrier based paints. The thickness of the coating seems to make it less prone to immediately flaking off once surface damage occurs with the risk of trapping moisture under the coating once you have incurred that surface damage. That seemed to be the take away conclusion from the TVR corrosion problem.

There are different formulations for the powders including epoxies, polyurethanes and polyesters so in that sense they are similar to 'liquid' paint coatings. The difference is the application technique and the chemistry associated with the setting process which allows for a much thicker application. As an observation, if you think that the hard finish, heavy bodied 2K epoxy paints are the hot ticket for your underbody protection their thick coating may make them susceptible to the same 'trap water under the coating' problem as the powder coat finish.

The Zinga product looks interesting and is available in an aerosol can form which is enticing. However, in Canada its only available if you want to purchase a 12 pack of cans. Not the hot ticket if you want to try a small test run first.

[Burdekin]

Zinc and aluminium epoxies offer good corrosion protection but don’t adhere as well to the substrate and aren’t as flexible. I prefer just a epoxy mastic. What I applied to my Amazon which I’m taking off at the moment and is still tough and not easy to get off:

3 coats of Jotamastic 80
2 coats of gravitex
2 coats of Jotun Hardtop XP

I’ll use Raptor and Jotun Hardtop AX next time.

[Derek UK]

PC for chassis, given a large enough oven, is fine. You can even drop it in a galvanising bath. However, for an up and running fully upholstered car etc any oven that is above normal paint oven temps isn't a place it wants to be.

[Bracpan]

Originally Posted by Derek UK

PC for chassis, given a large enough oven, is fine. You can even drop it in a galvanising bath. However, for an up and running fully upholstered car etc any oven that is above normal paint oven temps isn't a place it wants to be.

I know of someone building an oven big enough for a car chassis right now.
But as you rightly said the car would have to be stripped as the temperature of the oven would melt any plastic or rubber including the wiring harness..
And even after that you would get a beautiful shinny surface that will chip once a sharp stone hits it and cant easily be repaired... i know as ive just had parts done. Once the water gets under the coating thats the end of it as it will peel off.
There are a lot better ways of protecting the underneath of a car.
I tried some POR15 the other day on clean metal (no rust) the finish was amazing no brush marks and super tough once dried.. but there are many other paints that im sure would do a great job.

[Army]

Originally Posted by Bracpan

...
There are a lot better ways of protecting the underneath of a car.
I tried some POR15 the other day on clean metal (no rust) the finish was amazing no brush marks and super tough once dried.. but there are many other paints that im sure would do a great job.

My experiences of POR15 haven't been so great. For a single component solution I think Hammerite is better (though you need to make sure you don't mix the MEK based Hammerite with "normal" automotive paint types to avoid unwanted reactions).

About ten years ago when I started to pull my Mercedes W123 to bits I went through the whole POR-15 (and a similar product called KBS) "system" of using the special degreaser and then the special rust remover treatment and then the POR-15 paint and then the special tie coat primer and top coats...

...after about 3 to 5 years the POR-15 paint was very hard and brittle. It would chip off parts such as suspension bits. On the body parts (such as inner wheel arches) it failed to stop the rust in several places (and the car had just been sitting - it wasn't even used).

[DIsclaimer - I'm sure you or others coiuld say there was a problem with my efforts of preparation and execution and that it isn't the "fault" of the product]

I think my biggest complaint about POR-15 is the advertising that they used back then which was something along the lines of "stops rust forever". I'm not a believer. It was a bit like a garden shredder - promises a lot - fails to deliver.

#####

If you are looking for a single component product may I recommend a look at the Eastwood product range. Again - I don't think any stop rust for good claims should be taken too seriously.

For a cost and convenience single component solution I don't think you can beat Hammerite for parts that are not in a place where they need a hard wearing finish.

#####

I believe I have posted this before on this forum but here it is again =>

https://www.oldtimerautosite.nl/roest_test_2.htm

^^^^ This is a test of many products made by some bloke in Holland - it is all in Dutch so you might need to employ an online translation function (or ask me) if you get stuck with the lingo ^^^^

Results as of 2018

https://www.oldtimerautosite.nl/upda...1_juni__20.htm

(The links for the results are at the bottom of the page I first linked)

(Note it kinda backs up my not so popular claims about Hammerite - which on some forums seems to be hated as much as xenophibic biggots should be hated)

[Burdekin]

Originally Posted by Army

My experiences of POR15 haven't been so great. For a single component solution I think Hammerite is better (though you need to make sure you don't mix the MEK based Hammerite with "normal" automotive paint types to avoid unwanted reactions).

About ten years ago when I started to pull my Mercedes W123 to bits I went through the whole POR-15 (and a similar product called KBS) "system" of using the special degreaser and then the special rust remover treatment and then the POR-15 paint and then the special tie coat primer and top coats...

...after about 3 to 5 years the POR-15 paint was very hard and brittle. It would chip off parts such as suspension bits. On the body parts (such as inner wheel arches) it failed to stop the rust in several places (and the car had just been sitting - it wasn't even used).

[DIsclaimer - I'm sure you or others coiuld say there was a problem with my efforts of preparation and execution and that it isn't the "fault" of the product]

I think my biggest complaint about POR-15 is the advertising that they used back then which was something along the lines of "stops rust forever". I'm not a believer. It was a bit like a garden shredder - promises a lot - fails to deliver.

#####

If you are looking for a single component product may I recommend a look at the Eastwood product range. Again - I don't think any stop rust for good claims should be taken too seriously.

For a cost and convenience single component solution I don't think you can beat Hammerite for parts that are not in a place where they need a hard wearing finish.

#####

I believe I have posted this before on this forum but here it is again =>

https://www.oldtimerautosite.nl/roest_test_2.htm

^^^^ This is a test of many products made by some bloke in Holland - it is all in Dutch so you might need to employ an online translation function (or ask me) if you get stuck with the lingo ^^^^

Results as of 2018

https://www.oldtimerautosite.nl/upda...1_juni__20.htm

(The links for the results are at the bottom of the page I first linked)

(Note it kinda backs up my not so popular claims about Hammerite - which on some forums seems to be hated as much as xenophibic biggots should be hated)

I had the same experience with POR15, after a couple of years it just delaminates. Being single pack when does it stop curing?

Jotun Jotamastic 80 and 87 isn't expensive and are excellent. Lechler is another good epoxy primer.

[Army]

Originally Posted by 142 Guy

...
The Zinga product looks interesting and is available in an aerosol can form which is enticing. However, in Canada its only available if you want to purchase a 12 pack of cans. Not the hot ticket if you want to try a small test run first.

Shame they won't split a box for you - have you tried whinging / asking?

I think Rustoleum which I guess is more available where you are do a product that is similar (don't get fooled by the zinc-like-effect spray they also do - that's not the same).

Essentially "any" product that helps you apply zinc onto steel should have the same effect as Zinga I guess.

####

Further aside:-


The other reason for my appreciation of Zinga (particularly in a spray can) is that it is really handy for sheet metal working.

When I'm hammering and sheet metal forming I often start with warm zinc plated steel sheets because the galvanising process makes the sheet a bit softer than normal blank sheets and they don't rust so quickly in storage. After some bashing the zinc coating effect is somewhat altered (!) and if like me you get distracted by other things projects get to sit about for a long time. A quick spray of zinga over the work piece is ideal to stop corrosion.

It is also ideal stuff for spot welded structures - sprayed on either side (and then with bits carefully scraoped away where you are going to spot weld) it provides "in seam" protection.

I have heard of people using it as a weld through primer - this is a bit dodgy as there are serious (SERIOUS) health hazzards when trying to weld through zinc...

...that's another downside to using ZInga (or any other galvanised steel products) that you really really should remove the zinc before welding steel.

[Army]

Originally Posted by Burdekin

I had the same experience with POR15, after a couple of years it just delaminates. Being single pack when does it stop curing?

Jotun Jotamastic 80 and 87 isn't expensive and are excellent. Lechler is another good epoxy primer.

I've heard others saying the same about POR-15

Curing is usually a function of temperature and time - but I have no idea whether it would be months or years for that product.

####

Here in the Benelux countries I've been playing with Epifanes => boat products. Their epoxy primer has a zinc content apparently. One thing is for sure - mix the 2 components correctly - and that stuff will stick to everything (and will probably find its way onto everything!)

There's also another company called Poly Service here that provides (2 component marine grade) epoxy products. Their stuff in particular their panterscoating which is used to help bond normal car paints to epoxy is great stuff. (Well it seems to be performing well so far)

I do think epoxy solutions are the best solutions that are available at the moment: But who knows may be in ten years time I'll be banging on about a different solution...

[Burdekin]

Originally Posted by Army

I've heard others saying the same about POR-15

Curing is usually a function of temperature and time - but I have no idea whether it would be months or years for that product.

####

Here in the Benelux countries I've been playing with Epifanes => boat products. Their epoxy primer has a zinc content apparently. One thing is for sure - mix the 2 components correctly - and that stuff will stick to everything (and will probably find its way onto everything!)

There's also another company called Poly Service here that provides (2 component marine grade) epoxy products. Their stuff in particular their panterscoating which is used to help bond normal car paints to epoxy is great stuff. (Well it seems to be performing well so far)

I do think epoxy solutions are the best solutions that are available at the moment: But who knows may be in ten years time I'll be banging on about a different solution...

Surface profile and cleanliness play a large part in primer longevity as well.

[Bob Meadows]

I've used hot zinc spraying for chassis & suspension parts:~

A little specialized I suppose but I used a metal spraying firm in Liverpool-now closed- and more recently a boat restorer (barges) in Wigan.
They media blast and then spray the zinc on via a sort of flame spray gun, you can then follow through with a paint process of you choice- I use a zinc rich primer then a top coat.
Had the Riley chassis & most of suspension/some engine parts done back in the 80s it has never shown any rust since- probably not suitable for body panels but certainly worth considering for other parts.
I'm not keen on the powder coating process as a lot of parts seem to deteriorate quickly (flaking) the exception being original coatings on Volvo wheels-240
Hope it helps
Bob.