Cold Gal as undercoat

[gerg 10,871]

For body/paint experts:

 

I work with zinc-rich primer all the time at work and I think it's amazing stuff. I use it for the obvious rust treatment/prevention, etc but also on exhausts and steel-to-steel sliding sections as a dry-lube. I really like it but....

 

My question is, why can't you use it as a body primer on the whole car? It seems to bond really well with the steel surface and acts like an anode, meaning rust is non-existent as long as the paint's there (as opposed to other acrylic paints that bubble and trap moisture underneath). Is there a compatibility problem with automotive type paints?

[2redrovers 21,400]

Someone with more paint experience can correct me if I'm wrong, but as I understand it cold gal / zinc isn't what you would call a stable surface. The nature of zinc as a self sacrificing agent to prevent rust by converting to zinc oxides would mean that paint layer over the top wouldn't get the solid anchor hold it needs to bond permanently. Eventually as the zinc began to break down under the paint, it would create powdery oxide layer and allow the top coat to bubble and peel off. It would happen slower under paint than an exposed zinc surface but would still happen.

 

I believe you can use turpentine based paints over zinc rich coatings, but it's still not truly long-term adhesion.

 

(no offence taken if I'm incorrect)

[gerg 10,871]

That's a very good explanation and makes sense.. It does go powdery but I prefer that in critical areas like plenums and sills, etc where a normal acrylic or 2-pack would flake and rust through in small areas. As you mentioned also, it's a sacrificial coating so maybe it should be treated like antifouling on a boat?

 

Ever noticed on really old cars that had auto lacquer (ie up to early 60s cars) that the paint goes powdery and panels get a patina of thin hazy rust as opposed to post-1970 cars that get terrible cancer in critical spots even though the paint is still shiny?

[adrianphu123 73]

I used cold gal on my headers, then coated with high temp exhaust paint, all from bunnings and its held up really well for over a year now

[2redrovers 21,400]

With the old cars, further back you go the more likely that it's enamel paints. You get the nice patina from enamel because as it ages and degrades, it powders up with a chalky oxide an slowly falls away. A lot of metals were used in oxide forms to generate the pigments and flow characteristics of enamel, some of which I'm sure were zinc which would have helped protect the metal along the way.

 

Later paint is acrylic and then 2k, which will go porous as it breaks down, allowing moisture to penetrate. Because the paint is more like a plastic sheet covering the panel, it keeps its structure longer, trapping the moisture under the surface and allows deep rust to grow. Eventually the paint looses its ability to hold together and flakes off instead of powdering off.

 

I think the high temp paint is more like an enamel base too. When you add in the heat cycling I think you'll find that the cold gal isn't behaving the same way any more and would have a different bond and degradation effect.

 

When they say it's not a suitable base, it's not that it won't work or that it won't work for a while, it's more that the results are not able to be guaranteed to give you what you want. There's a lot of variables and sometimes it will work ok, others will be disastrous results that haunt you no matter what you do with it.

[gerg 10,871]

That's pretty much what I thought about all of it except you explained it very well (much better than I could)... Cheers redrover

[2redrovers 21,400]

No worries mate. I've been wanting to pick your brain on another topic and while we're chatting amongst ourselves...

 

Have you got any design ideas that could be applied to an xc sedan? I'm liking where you want to take your coupe but I didn't think the same philosophy would work on a sedan. Any thoughts?

[gerg 10,871]

Sedans are harder to make sleek but personally, one thing I don't like about XCs is the window line at the back door to the pillar. It's more squared off like an early Granada (an attempt to lead-in to the square Falcons) whereas XAs and XBs have the coke-bottle hip line, much more curvy and fitting with the rest of the car. I find the quad light front more attractive than the rectangular one.

 

Depending on how extreme you want to go, you could lay back the windscreen and same for the rear window. Rear pillar could be thinned down at the top to suit the laid-down glass but keep the same line on the door frame. Side glass could be a problem on the front though, maybe get some rear door glass, swap sides and install in front with custom front quarter glass like a smoker's window.

 

You could look to some exotic European sedans of the era for inspiration, like the Maserati quattroporte or De Tomaso Longchamp, even Jag XJs.

 

I'd delete bumpers and fab custom bodywork to fill in the gaps, then put some more delicate ones on that wrap nicely around each end of the car, like on an E-type Jag.

 

Cut out and fill wheel arch swages and re-profile the rear to match the front. (70s Falcons look like bum-draggers)

 

Overall I think it could be a very handsome car if done tastefully and with period styling cues.

[2redrovers 21,400]

Good ideas there and you took it in the direction I had in my fuzzy head. The painter I'm doing the torana for has an xc sedan he got cheap and we've been talking over ideas on what to do with it.

 

I've had crazy thoughts on doing a pillarless rear suicide conversion like the Lincoln continental. I wanted to tweak the rear pillar somehow but hadn't had a chance to look into it yet. We both thought about the quad lights, but I've been looking for a solution that fits with a slim bumper and doesn't just look like an Xb jammed in there.

 

Personally I'm ok with turning it into something totally different, maybe like a phantom ford prototype but not necessarily recognised as an xc. I'll see if I can transfer some of what you suggested to a digital mock-up and we'll see how it looks.

[2redrovers 21,400]

Ok, had a little time to fiddle with a side on pic. Not finished so I can't put it up yet but found the back window swap won't work and a straight up solution. You either have to cant the B pillar forward or cut the glass up to make it fit in the upper front roof line.

 

Next thought I had while tweaking things around was pillarless using modded coupe doors and a three quarter rear opening suicide style.

[gerg 10,871]

I was thinking more along the lines of a pie-cut down the length of the pillar to lay the glass flatter but retain the side window line. If you think it can't be done then I trust you... You're the body man, I'm just a diesel mechanic :-D

[2redrovers 21,400]

I realised after I posted that it might not say what I meant.

Your right with the rear windscreen, that will work fine. By rear window swap I meant your idea for the side glass. On the computer at least, when you line up rear door glass into front door opening the top edge runs too far uphill. You might be able to grind back the glass and make it fit, not sure if it would survive that process though.

 

Where I left it last night I had lined up the rear window into the front door space which made the door about as long as a coupe. This had the upper B pillar leaning forward and I thought it didn't look too bad. So move the pillar back and swap sides on the upper half. Use coupe door with the rear edge of a sedan doorskin spliced on to keep the right line. Use coupe door glass up front. Rework rear sedan door to open backwards like an rx8. End up with B and C pillar lines about same angle with the adjusted rear screen angle.

[2redrovers 21,400]

Please ignore some of the dodgy aspects of my photoshop skills, this was the first time I've actually managed to work out what to do with the program.

 

Before

After

 

This would not be a small undertaking to make it a reality......fun though.

[2redrovers 21,400]

This is one direction I think the rear end could go, 70/71 torino

 

The other idea I had was working in tail lights from xb ute. Would have the same shape as the new rear quarters, maybe with a coupe boot lid and a reworked back panel.

[gerg 10,871]

That modded pic you did looks pretty sweet, a bit like a Cuda. The pie-cut on the c-pillar works well. I think it needs at least bumperettes otherwise it will start to look like an 80s pro-street tragic, unless that's what you want.

 

It needs to have the rear wheelarch raised an inch or two so when you even out the front/rear stance, it doesn't look like it's got a saggy arse.

[gerg 10,871]

This is one direction I think the rear end could go, 70/71 torino

 

 

The other idea I had was working in tail lights from xb ute. Would have the same shape as the new rear quarters, maybe with a coupe boot lid and a reworked back panel.

 

The Torinos remind me of ZG and ZH Fairlanes a bit, maybe some panels from them would be an easy fit. The doors are the same anyway.

 

Ute/wagon tail lights would be interesting, or maybe something like Maserati 3200 GT lights (ie hockey stick) what about some old Mercedes tail clusters? Rover SD1? (Lotus Esprit used them)

 

Good luck finding a coupe bootlid, or coupe anything really.

[2redrovers 21,400]

Yeah haven't worked out what bumpers to use, was thinking something that only just wraps a little around the corner of the body. Or maybe one that ends in line with the body.

 

Might not be able to pick it but I did raise the rear wheel arch by about an inch or a bit more. In reality it may need more that to look right. I also raised the top line of the quarter to flow with the pillar. It was an unexpected change but I liked the way it looked in this version.

 

Haven't figured out if I just lifted the quarters so I guess it would have fins of sorts, or if I also raised the boot lid and whole rear panels. I think the second.

[2redrovers 21,400]

Before I did the pic I'd thought maybe triple round tail lights but I like the thought of the hockey stick shape too. I noticed the similarities to z fairlanes, could be modded to get the rear quarters and maybe boot too.

 

We all know half this car would be hand made, although Gerry has some coupe parts just laying around

[bear351c 10,271]

XA,B,C ute and PV had a similar glass shape on the side windows, also early XA still had vent windows on the front doors, rare, but can be found.

Like the photshop, need to weld up the back door. LOL....

 

 

Pillarless would look awesome, a bit Torino like. Maybe the front door should be a few inches longer.?

[bear351c 10,271]

Thread hijacked, by Bear. 

 

Sorry dude. Know nothing about painting over cold galv. Good shit, that. 

[gerg 10,871]

Lol should be the "off-topic paint and body thread"

[2redrovers 21,400]

Thread hijacked, by Bear.

 

You're a bit late

 

Maybe it should be renamed the "theoretical body design, with a bit of tech info on cold gal" thread

 

EDIT: I'd be more than happy if we made a body design thread and moved all my ravings to it instead of crowding up gerg's. It's becoming clear this will be an ongoing topic.

[bear351c 10,271]

Yeah, you could be right.........

[2redrovers 21,400]

Design thread started