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MG Midget and Sprite General - Epoxy primer. Waterproof?

I'm awaiting the arrival of a bodyshell back from media blasting and they will coat it with anything I ask for. Is there a primer system that remains waterproof? I've initially suggested Etch and then a zinc cellulose but am wondering if there is anything that will keep moisture off until after the lead loading has been carried out at home.

Any thoughts or suggestions for a product in the UK?

Cheers.
rob thomas

Rob,
I have recently primed an engine bay which I had first taken back to bare metal. I then used etch primer on the bare metal and then sprayed an epoxy primer known as 'Direct'. This provides a totally waterproof coating. I now have the choice to either apply a 2k primer and top coat or could just go straight to the topcoat. An experienced paint sprayer friend of mine kindly supplied the product. Not sure where he got it from but I believe it is available from paint suppliers. I doubt it will be cheap but am assured it is very effective.


Neil K

Neil

naughty chap, chap

Every time I see a body like that ready to fill with prime machinery and succulent paint

I get all twitchy :(

I think etch primer ought to do the trick perfectly, if i has the treatment Neil has had on his car
Bill 1

Hiya Bill,
How are you?
Lara needing some paint then?
My friend told me that etch primer is brilliant at treating bare metal but it won't prevent water penetration. A further primer is necessary. Epoxy primer is good provided the vehicle is kept in the dry. However if the car is exposed to dampness whilst still in primer, the primer will absorb this moisture. This 'Direct' product however will not. It is totally waterproof. We'll soon see as the Midget I am currently restoring is in the carport at the moment and exposed to the damp. I used the 'Direct' as I am not ready to apply the top coat yet.

By the way, the engine bay was like this before I stripped back to bare metal and primed.

Neil K

Oh yeah and then this

Neil K

I should clarify that the 'Direct' product was polyurethane based and not epoxy as I stated in my first reply.
Neil K

Hi Neil,
Is the name "Direct" the product or the manufacturer's name? Can you get details from your paint buddy - it sounds like the ideal stuff!
Guy

Guy,
I have spoken to my friend and he has given me more information. He explained that the product is called Sellimix Direct Adhesion, a product made by PPG. It is essentially an industrial product but which can be used in the automotive arena. This product is not only waterproof but is UV resistant. He said that he was involved in a test whereby two pieces of metal were sprayed, one with etch primer and epoxy primer and the other with etch primer and 'Direct'. They were both submerged in sea water and left for six months.When examined, neither piece of metal showed any signs of corrosion. However the 'Direct' has the advantage of being UV resistant.
In light of this additinal information, I would say that epoxy primer would be fine. It does however have a tendency to shrink back if exposed to the sun for any lengthy period and before it receives its top coat. This won't happen with 'Direct'.
This may assist:
http://www.ppg.com/coatings/selemix/en/Product/Pages/225_Selemix_system.aspx
Neil K

Neil

No mate Lara is green enough as she is

for now

Anmd thanks for showing the before picture

Now I don't fancy it again, at all :)

That does sound like the business to use though, I hear the thoughts stirring all over after that first picture

:)
Bill 1

Thanks Neil,
Not quite ready for it yet, but will keep this for future reference!
Guy

Just to come back on this topic,
What are the relative merits of a Polyurethane primer as against an Epoxy based one?

I discover that I have already bought some small sample tins of an Epoxy primer from these people: http://www.rust.co.uk/epoxy-mastic.cfm

Not used any of it yet. I only bought it just before Christmas and had completely forgotten I had it! It is going onto the inside surface of my newly repaired rear wing before it gets welded in place after which I won't be able to get at it when I spray the whole body tub at some future date.
Guy

I have used an epoxy 2k primer for the insides of my wings directly on top of jenolited bare metal.

This with some waxoyl is all it's getting.

If the primer is applied in a couple of coats -it is fully waterproof.

Jon

Jon White

Guy,
My understanding is that both poly and epoxy are waterprrof and so there is no issue there. I guess it's to do with what application it is being used for. Poly is more an industrial based product and as such may withstand more extreme conditions, but this is just what I have been told. I used poly as I was told that as I wasn't ready to spray my top coat on for some time, the poly wouldn't shrink back if the car was outside in the elements. Also I was giwen it as it was left over from a job and so I didn't have to go and buy epoxy primer.

Jon,
I know you say that the epoxy primer is waterproof and I agree with you, it may not be chip proof however. The exposed area under the wings get a hammering. Therefore personally I would give a further coat of stonechip on top of your primer followed by a top coat of your finished paint colour. But that's just me.

Oh Yeah and where is Rob, he started this thread!!!!
Neil K

The supplier of what I have says it doesn't shrink back, and is waterproof. They also make great claims about its ability to "flow" into micro-pores and therefore bond better without allowing rust to spread beneath it if it does chip.

In my case, it won't be exposed to chipping from road debris, but I am wanting to weld the panel in later so I need to use something with a high melting point once cured. I will do the weld-contact edges with weld-through primer and then mask over before using the epoxy primer, but there is still bound to be a certain amount of heating of the adjoining metal.

I am going to use this stuff anyway - as I have got it. I will decide later between epoxy or poly when it comes to priming the whole tub.

I will definitely again use a stone chip on the whole of the underside. Next time I will also stone chip the floor surfaces inside. It is surprising how much wear and tear the floors get under a set of carpets or mats.
Guy

OK, another (related) question.
I have given the inside of the wing a first coat of phosphoric acid treatment. This was after blasting it back to mostly bright steel. When that has hardened I will give it a couple of coats of the epoxy primer.

But I am a little bothered about how well bonded the phosphate layer will be? Should I re-wet it with a second coat of the acid and then immediately wipe the surface so that it only remains where it has actually bonded to any rust particles? Or will it have bonded to the bright steel as well?

I have done this stuff before, but never quite with this combination of materials so I am experimenting a bit to get the best technique.
Guy

This thread was discussed between 22/03/2011 and 28/03/2011

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