Lotus Elan

Painting bits

PostPost by: JonB » Thu Oct 24, 2019 8:06 pm

You probably saw some pictures I posted of the air box on my car. Looked pretty good in matt black, but that?s an undercoat. I?ve sprayed all those parts gloss now, and they look OK. Not perfect but good enough.

c33ed3f5-f3e0-43fb-994a-f6aa07c145e3.jpeg and
Airbox


aadc75e1-6d54-42b9-bfef-8a4d300ef788.jpeg
Carb intake casing
aadc75e1-6d54-42b9-bfef-8a4d300ef788.jpeg (39.78 KiB) Viewed 1155 times


These look reasonable. However when I tried to paint the intake cove it was a different story.

6f4ede7e-2ad7-4004-8e50-88f8dbbc0038.jpeg and
Plenum cover


It looked ok when the paint was applied, but dried mottled. What have I done wrong? Any ideas? The cover is fibre glass with a black gel coat, and although you can polish this to a reasonable shine, there are too many imperfections on mine for it to look decent. So I thought to paint it, and rubbed it down to give a key, then one coat of matte. Once that dried, I laid down a coat of gloss.

I?ll rub it down tomorrow and give it another try, but I?m curious as to what might have gone wrong.
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PostPost by: MarkDa » Thu Oct 24, 2019 11:50 pm

It will be some sort of paint I compatibility - I had something similar on mine.
I'm very impressed with the high build Matt paint.
I'm going to redo some of my parts that aren't as good as they could be with it - starting with the Spyder adjustable rear wishbone that looked to be reasonable when I bought them but are distinctly in need of work after a couple of years on the car.
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PostPost by: alanr » Fri Oct 25, 2019 9:17 am

What sort of primer are you using before the top coat?....In my experience paint applied without a good primer doesn't last long and soon chips off.
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PostPost by: JonB » Fri Oct 25, 2019 9:56 am

It?s a Screwfix product called No Nonsense Matt Black. I used it on the metal parts with no problems. Topcoat is also No Nonsense but gloss black. I think they are acrylic paints.
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PostPost by: alanr » Fri Oct 25, 2019 10:07 am

Hi Jon,
Just looked on the Screwfix website and it does say that the stuff you are using is not a combined primer/topcoat and needs a primer. This I believe is your problem.
Quote from Screwfix:-
'This is not a combined paint and primer. It can be applied to bare metal but the surface should be fully prepared before hand (cleaned, rust, dirt and oil removed etc).

For the best possible finish a red oxide primer can be used.'

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PostPost by: 2cams70 » Fri Oct 25, 2019 11:29 am

How much time did you leave between finishing the primer coat and applying the top coat? My experience with rattle can painting is that this is important. Begin applying the top coat when the solvents in the primer coat have only just flashed off (typically around 15minutes) that way the primer coat is soft enough to allow the top coat to bond well with it and the primer coat still has sufficient flexibility to move about on the underlying substrate and shrink if necessary to accommodate the topcoat shrinking whilst drying without it crinkling up. If you allow an intermediate time the primer coat will not have sufficient flexibility and it also will have not have had sufficient time to develop firm adhesion to the substrate - hence the crinkling. If you leave the primer coat a very long time so it is fully cured (i.e several days) you may be in a better situation because by that time it may have developed strong enough adhesion to the substrate so the effects of top coat shrinkage don't present themselves. Best procedure is to apply top coat soon after last primer coat in my experience. It goes without saying that the chemistry of the top and primer coats need to be compatible with each other otherwise nothing will help!

Note the scientific explanation is all theory on my part - I'm no expert on paints!
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PostPost by: vincereynard » Fri Oct 25, 2019 1:52 pm

Jon
If you want originallity I believe the airbox should be satin black.

s3750001.jpg and


I fitted mine by smearing a coat of silicone grease on the metal and laying a bead of black (fuel proof) mastic on the airbox.
Wait a bit until it has a touchable surface then screw lightly together.
Tighten when the mastic has cured. "Instant" rubber gasket. (Hopefully.)
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PostPost by: JonB » Fri Oct 25, 2019 5:20 pm

Thanks, Vince... I gave it another coat and it came up very shiny. Too shiny! Will take it to satin in due course.
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PostPost by: derek uk » Sun Oct 27, 2019 11:16 am

I've been using Simonize Tough Black. Low gloss but with a smoother finish than a lot of the satin paint's. Multi buys on the bay are well priced. Eastwood have their good but expensive "under hood black" That works well.

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PostPost by: jono » Mon Oct 28, 2019 10:22 am

I painted my airbox backplate with VHT wrinkle finish - not standard but it looked great.

What I found with cheap acrylic rattle cans is if you had a fuel leak the paint came straight off - the wrinkle paint seems to be fuel proof.
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PostPost by: JonB » Mon Oct 28, 2019 11:31 am

Ah, OK. I see a test in the near future. As I have sprayed it all with acrylic! :(
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PostPost by: JonB » Mon Oct 28, 2019 5:17 pm

img_6167.jpg and


This was the result of my test with a petrol soaked rag. The paint dissolved almost immediately. :evil:

Four tins of Simoniz Tough Black on order! The other paints are going back to Halfords / Screwfix! I'm particularly annoyed by the Halfords paints as one might assume they'd be for automotive use. Bah. :evil:
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PostPost by: alanr » Mon Oct 28, 2019 5:29 pm

Jon,
I fear without using a primer first on bare metal most paint will do the same...

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