Epoxy Primer

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Chris Waite Chris Waite
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Epoxy Primer

This is aimed at John Perry

And anyone else who knows better than I do, (which should include most adults and many children).

People, that's you guys, keep talking about Epoxy Primer and I understand that (John Perry's) Grey Boat  is that colour because it never got any further - yes?  I'm not looking to prime anything and I've used two-part polyurethane gloss topcoat straight onto the usual clear (two-part) epoxy goo we all use for aiding and abetting plywood; two coats cover the epoxy with no problem and have yet to peel off.  It really is the ultimate plastic coat to protect our creations - only fading, scratching and boredom give any good reason to ever need to repaint.

No, I'm into subdued senior shades of matt now - grey in fact.  Epoxy primer seems to fit the bill and is perhaps harder wearing than the matt two-part polyurethane I have used most recently on Polly Wee.  The matt stuff just doesn't seem as durable as the gloss; or maybe I'm just clumsier in my dotage.

So, is epoxy primer epoxy based and if so

Why doesn't it wither

In the sun?

CW  
Paul (admin) Paul (admin)
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Re: Epoxy Primer

Jotun HB Primer is a grey epoxy primer suitable for lining potable water tanks. That makes me think it is both waterproof and stable.

It certainly stuck very well to my epoxied hull over 10 years ago. But I did add polyurethane/epoxy twin pack top coat - Signal Red.

I suspect your perfect solution is adding a shiny grey top coat, instead of just the matt grey primer.

However being epoxy based the primer can last very well, with touching up, as John will testify. That gives you a long time to chose the name, turn it into a row boat etc.

cheers
Paul
Say NO to Brexit. Kick it into the long grass
John P John P
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Re: Epoxy Primer

In reply to this post by Chris Waite
Chris - I am no expert on painting!  

Yes, for some years epoxy primer was acting as the top coat on our sailing dinghy but since then I have sanded it down, I think I then added another coat of epoxy primer, more sanding and a two pack polyurethane top coat.  Its been like that for a couple of years and is fine apart from minor scratches underneath, which I suppose I should do something about before we go sailing this year.

Its quite an old boat now, built 1978, and its had many coats of paint over the years, using a variety of different paint types including house paint as well as paints from yacht chandlers. Also one year I put anti-fouling paint on it expecting to have it afloat for a few months continuously. I wouldnt do that again unless I was sure the boat was going to be afloat for much of each summer since it is so hard to get rid of completely - there are still patches of antifouling paint deep down and I suspect that is not good for the adhesion of the later  paint layers.  If you do get a few barnicles on a sailing dinghy after an extended holiday afloat its easy enough to roll the boat on its side to scrape them off.

Thinking of paint for the row boat I am building, I will start with Jotun Pengaurd expoxy primer since I know that is good for sanding smooth and also I already have a can of it, so no choice really. Not sure about topcoat on that. Maybe a good house paint - the boat will not be kept afloat for long periods and will probably be stored under a cover. We havent decided on a color, other than it will not be grey, and house paints come in a much wider range of colors than marine paint. Some say house paint is just as good anyway.  I suspect it probably isn't, but it may well be quite good enough.

inwe inwe
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Re: Epoxy Primer

Don't forget that house paint is no longer oil based. I used epoxy 2 pack on the red submarine last year and its as hard as he... kitchen steps. Good luck Chris.

Richard
Port-Na-Storm Port-Na-Storm
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Re: Epoxy Primer

From what I can see during a brief trip round the web looking at info on JOTUN, epoxy primer is not UV resistant.
Epoxy two pack and polyurethane two pack are different things.

In a blatant case of "do what I say don't do what I do" I'd say use the specific primer to match the top coat you plan to use. Doing otherwise is like trying to spread marmite on top of butter.

I agree matt finishes don't seem to be as resilient as gloss, I think this is partly because gloss reflects sunlight and therefore UV much better, the hard gloss finish also helps to shed water and dirt.

Last year I painted my garage doors with Valspar metal & wood exterior paint from B&Q. I used the correct primer, its flaking off already.
Paul (admin) Paul (admin)
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Re: Epoxy Primer

In reply to this post by John P
John
If you go to the trouble of using a 2 pack primer, you can add a 2 pack top coat and get upwards of 10 years protection.

As Richard eluded modern household paints are low VOC and brushes water washable, if possible.
They tend to leave a thin coat and abrade away.

Compare that to the 1970s heavy-duty gloss that left a thick tough coat. I can point to some rock solid door frames my dear Dad painted all those years ago.
The only problem was 3 days of toxic solvent to breathe in...but who cared then.

I'm extremely pleased with the 2 pack polyurethane top coat on MilliBee's hull. It has lasted 10 years, the colour is strong and it is only damaged where rusty bolts have dragged along the hull.

After all the hard work sanding and fairing the hull, it's just a few extra hours to add a polyurethane top coat.

At Jotun there was a good range of colours to choose from - cost varies according to the amount of pigments required.

Cheers
Paul
Say NO to Brexit. Kick it into the long grass
Paul (admin) Paul (admin)
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Re: Epoxy Primer

The critical issue, explained by the professional paint tech when I bought Jotun, is that Jotun HB Penguard is epoxy based and therefore sticks very well to epoxy coated wood/glassfibre cloth. (HB stands for high build, filling minor stratches).

Where I have used the HB primer the paint system has been rock solid. I have very little evidence the HB primer has detached from the wood. There is one spot around a tabernacle bolt - highly compressed and the silicone hardened and pulled both paint layers away from the epoxy when I knocked the tabernacle free for maintenance. I think I had to tap a flat blade under the tabernacle to free it. The epoxy is shiny, perhaps I did not sand it enough? That was the weak point in the system.

Where I forgot to use the HB primer, the 2 pack polyurethane top coat has not done well the last 10 years; it tends to detach from the epoxy/wood.

So definitely go for a 2 pack epoxy undercoat on a well sanded epoxy coated hull. It will be an excellent undercoat for any topcoat.

As for colour, West recommend white as it reflects the most UV and therefore gives the best protection.

-Paul
Say NO to Brexit. Kick it into the long grass
Chris Waite Chris Waite
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Re: Epoxy Primer

Should have done this originally, of course....

I've just checked the horse's mouth and this is how it goes -

1.  According to Jotun, (their) epoxy primer is, you guessed it, epoxy based - for use on substrates other than epoxy, where it is not necessary.  Though if the epoxy is more than a few days old, it should be abraded before (for instance) applying a two part polyurethane paint.

2.  Being epoxy itself, it is subject to degradation by sunlight.

3.  You misunderstood Paulie - the grey on Polly Wee is not an undercoat, or primer; it is actually Jotun matt HB Topcoat.  The horse confirms this is not quite as scuff resistant as the gloss.

A pity, as in my dotage I have a slight yearning to fade stylishly into the middle distance.  It attracts less attention from those of a not entirely benign disposition, jobsworths and for instance, collectors of fees in arguably 'controlled' waters - corners of harbours and the like.

4.  White may be good on reflection, but it's a bit bright to be subtle and as you say, even an un-covered two part polyurethane lasts many years without losing its hue

Stop calling me Hugh

Camouflage next

Methinks

CW  
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