Primer... which is best for bare metal?

Technical advice Q&A

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Rich70
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#1 Primer... which is best for bare metal?

Post by Rich70 » Fri May 08, 2020 8:26 pm

I’m planning the paint stripping phase of my E-Type restoration and starting on the smaller panels before the main shell. When it comes to primer which is best? Epoxy, etching, high zinc.... I’m lost...

Rich
Richard. UK RHD 1970 S2 2+2 Auto.

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Tom W
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#2 Re: Primer... which is best for bare metal?

Post by Tom W » Fri May 08, 2020 8:53 pm

If the parts are due to sit in primer for a while, I’d pick something that’s non porous.
Tom
1970 S2 FHC

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cactusman
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#3 Re: Primer... which is best for bare metal?

Post by cactusman » Fri May 08, 2020 9:16 pm

If the parts are a bit rusty (not flaky though) dinitrol is worth painting on initially.....
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

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vee12eman
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#4 Re: Primer... which is best for bare metal?

Post by vee12eman » Fri May 08, 2020 10:53 pm

Hi Rich.

What I do is to spray or brush a rust converter such as POR 15 Metal Ready over the bare metal. Metal Ready is a phosphoric acid based substance. Jenolite is another I remember in UK. I won’t go into the debate about the whole POR 15 system, save to say, don’t use POR 15 paint for the purpose of temporary protection. (They recommend a clean beforehand with Marine Clean, another POR 15 product; any good de-greaser should be fine. Dry the surface of the cleaner, but don’t be too concerned at this stage as the acid actually contains some water anyway.)

Try not to allow the resulting coat of your phosphoric based converter to dry out, by re-application if necessary. If you’re just protecting bare, un-corroded steel, about ten minutes is fine. If you have a little corrosion, leave it longer, but in either case, keep it wet.

It will clean the metal, etch it slightly, then leave a surprisingly rust proof coating for a while. It won’t withstand prolonged direct moisture contact and I would not rely solely on it for protection in damp conditions. Wash it well afterwards (use a rag and water if you don’t want to get it, or the surrounding areas too wet) and dry it well. I like to get it out in the sun or sometimes use a very quick application of a propane torch to get the area warm enough that you see the moisture leave the surface, but no warmer; keep the flame moving and never in one spot for too long. You’ll have a light powdery coating in some places afterwards, white to orange in colour. Wipe it off carefully with a rag dampened very slightly with the acid/converter again, then remove all traces with a slightly damp cloth; using fresh water, but only slightly damp. Keep changing the contact face of the rag to lift as much as possible rather than leaving a residue. once it dries fully, you will probably still have a few small amounts of the residual powder, which I just remove with light rubbing using fine steel wool; don’t rub so hard you remove the phosphorus coating.

You can leave it at that for a short period, a few days or a week or two. I have occasionally left it much longer and been very pleased when I return. However, I’d recommend a coat of etch primer for further protection and if you want to leave it longer or if your storage might be damp, another coat of etch, followed by some conventional primer, I normally use a can of high build primer. This is fairly good protection, easy to remove when paint prep starts and, if you don’t get it all off at that stage, the new paint will sit happily on top provided you have keyed the whole surface well with production paper. When I make new panels or repair sections, I treat the new metal exactly the same way. You will notice changes at each stage; first the metal brightens, as the acid does it’s work. Very minor surface corrosion will simply disappear. Then the surface darkens, especially after washing. There may be a residue, as earlier described, if you allow the acid to dry before washing off, this will be worse.

If the panel won’t be seen, say the back of rear wings, then you can consider a thicker coat, for example, the POR15 mentioned earlier (which should not need a top coat, but should only be used where it isn’t exposed to sunlight or UV light). However, whilst I have had some very good results with POR 15 I’ve had poor experiences too, so maybe a good brushing primer, which varies from country to country, but be aware that some primer is suitable for oil, water or thinners based top coats only. Check compatibility with your intended top coat.

Ok, so this is a long answer to a simple question, sorry, that’s just my way. So I guess that a coat of etch primer, without all the above, would be my go to if time was pressing. The above process does provide a good surface however.

There are as many opinions on the best treatment as there are restorers, or so it seems, but that’s what works for me.

Regards,

Simon
Last edited by vee12eman on Fri May 08, 2020 11:12 pm, edited 1 time in total.

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Thor
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#5 Re: Primer... which is best for bare metal?

Post by Thor » Fri May 08, 2020 10:57 pm

Upol. do etching primer in aerosols great for small panels.it works the best. :Scotland:

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MarkRado
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#6 Re: Primer... which is best for bare metal?

Post by MarkRado » Sat May 09, 2020 4:56 am

Professional paintshops recommend 2pack epoxy, thats what I use, dont care for the brand, but make sure that you get the recipe for the product right (eg paint/hardener: 3:1, 15% thinner).
If I have to do a "dirty" repair on small areas (not all rust etc removed completely), I use an epoxy based rust converter (Brunox) first.
Mark
1963 OTS 880436

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Nick V12 e type
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#7 Re: Primer... which is best for bare metal?

Post by Nick V12 e type » Sun May 10, 2020 5:30 pm

Hi Rich,
I’m just stripping the underseal from my car and have decided to use Bilt Hamber rust gel where needed and then use their Zinc primer on the bare metal on the underside and within the sills etc as I’m replacing panels. It seems a zinc rich primer will give a good level of protection under the car and a stone chip coating will go over to finish the job.
Bilt Hamber products seen to have good reviews and I hope will keep the rust at bay.

Good luck

Nick
e type series 3 V12 2+2 1972, Tesla Model S 2016

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