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Reconditioning Subframes


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#1 Wired

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Posted 06 October 2005 - 11:29 AM

Hey !

Just got back on working on my mini, i've removed my subframes, , the rear one was all rusted, so i bought myself a new genuine one.

Im getting all arms and the front sub shotblasted, and givin a special metal coat (its called "metallisering" on danish, cant seam to fin a english word for it).

I want the ultimative rustproof subframes, What to do next..? Powder coating? Or just some special paint? what are the cons and pros.

And what should I do with the new rear subframe.. I've heard that its paint aint that good...

Please help a newb :tongue:

#2 minimadjonesy

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Posted 06 October 2005 - 11:51 AM

powder coat it!

#3 dklawson

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Posted 06 October 2005 - 12:10 PM

If available to you in Denmark, use POR-15 (sold by Frost in the U.K.) with a top coat of black epoxy paint.

Powder paint is great, but it chips and peels easily from flat surfaces (particularly ones subject to impact... like subframes). POR paint is a very tough, impact resistant paint. It's weakness is that there is a lot of preparation involved and the cured product discolors when exposed to sunlight. It can be topcoated with more traditional paints (like the epoxy) to achieve a long-lasting uniform color.

#4 Tarks

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Posted 06 October 2005 - 12:48 PM

galvanising???

#5 Wired

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Posted 06 October 2005 - 10:04 PM

If available to you in Denmark, use POR-15 (sold by Frost in the U.K.) with a top coat of black epoxy paint. 

Powder paint is great, but it chips and peels easily from flat surfaces (particularly ones subject to impact... like subframes).  POR paint is a very tough, impact resistant paint.  It's weakness is that there is a lot of preparation involved and the cured product discolors when exposed to sunlight.  It can be topcoated with more traditional paints (like the epoxy) to achieve a long-lasting uniform color.


No doubt.. I can get it.. If I understood it correctly, one bottomlayer of POR15 metal ready, and then a coat of POR15 Rust prevention, and a layer of chassis paint..?
Will that last long?

#6 mini_kev

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Posted 07 October 2005 - 06:06 PM

strip it bak to bare metal then paint about 3 coats of hammerite on it!!

#7 dklawson

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Posted 07 October 2005 - 08:48 PM

Hammerite (if it's what I buy over here) will still chip.

You'll get an application data sheet when you buy POR products. Succinctly, strip the part to remove all old paint and coatings. Wash the part using POR's "Marine Clean" degreaser. Remove the surface rust using whatever method you prefer and wash/rinse again. Treat the surface with POR's "Metal Ready" which is a phosphoric acid treatment. Keep the Metal Ready on the bare metal for a LONG time (making sure to keep it wet). You'll build up a grey coating of zinc phosphate. After you've got a good phosphate coating and the surface is completely dry, you apply two coats of POR paint allowing sufficient time between coats (see their instructions). After the second coat has almost dried but is still slightly tacky you apply a fog coat of primer. (Do not waste your time or money on POR's "Tie Coat" primer). Let the POR and your fog coat of primer dry for a day then come back and spray a nice coating of chassis paint. I use Eastwood's "Chassis Black".

POR can be sprayed but I suggest you use a VERY cheap spray gun. POR will cure on your skin and can't be removed with solvent. You have to wait a few days for it to wear off your skin. Be sure to wear gloves and clothes you don't care about.

Visit their web site for more info on the products:
www.por15.com
You may also want to look at the product description/application notes at:
http://www.por15.com...es/por15sum.pdf

#8 stormduck

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Posted 08 October 2005 - 10:12 AM

Excellent instructions mate, i'll use this method myself. Just one question, any old primer will do for the 'fog coat'? Is this just so the chassis black has something better to adhere to?

#9 dklawson

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Posted 08 October 2005 - 11:12 AM

The surface of cured POR-15 is almost like glass it's so smooth. This makes it hard for virtually any top coat to adhere. On most paints you'd sand the paint to give the top coat something to stick to. POR is a urethane-like coating and doesn't sand well. POR makes a special primer called Tie Coat that's formulated to adhere to the smooth POR paint. However, my experience with it is mixed and I don't like it much. In their instructions, POR mentions the fog coat of primer and this has worked better for me.

The purpose of using a fog coat instead of laying down a regular continuous film over the surface is to allow solvents to evaporate. This is VERY important with POR. I like the stuff but it's not as easy to apply as they lead you to believe. You MUST allow sufficient time between coats, and you must apply no more than a fog coat of primer, OR the paint applied on top will trap solvents in the bottom coats. The solvents have to get out and they make it to the surface as little pin-hole bubbles that ruin the protective film. Follow the POR instructions carefully regarding when to apply second coats. The fog coat of primer provides an anchor for the "real" coat of primer applied later yet it allows the solvents to escape.

Any primer compatible with your top coat paint will work. The Chassis Black paint I use is an epoxy with satin finish. It is compatible with spray-can type primers. The epoxy top coat protects the POR from UV light which will discolor POR.

I've noticed recently that POR has been used on some of the Mini World projects. I'll be happy to share my experiences with it. So far, three years on, I'm still happy with my results.

#10 pierce

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Posted 08 October 2005 - 11:34 AM

I paint mine with hamerite brush on smooth black then a coat of hamerite hammered finish spray then i use schutz with added wax oil

#11 stormduck

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Posted 08 October 2005 - 08:21 PM

The fog coat of primer provides an anchor for the "real" coat of primer applied later yet it allows the solvents to escape.

Excellent! What do you mean by the real coat of primer applied later? Surely it would be metal ready, por15, fog primer, chassis black? Isn't that enough!!!??? :grin:

#12 dklawson

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Posted 09 October 2005 - 02:00 AM

The fog coat is not a continuous coat of paint. If you put a continuous coat of primer on while the POR is still curing you'll trap solvents and create pin holes in the coating. If you wait until the POR has cured to apply a coat of regular primer, it's like you're puting the primer on glass and it won't stick well. The objective is to put a fog coat down on the tacky, still curing POR so that you're creating anchor points for a full coat of primer later. This prevents the formation of pin holes in the POR and produces a strong bond between the layers of paint.

#13 stormduck

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Posted 09 October 2005 - 03:45 PM

sweet, i'm with you now, i thought the fog coat would be sufficient enough to put the finishing coat on top. That's excellent, many thanks for that, i'll hopefully have bomb proof paint on my subframes in the next few weeks! Cheers!




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