GRP Primer - Zinc Phosphate?

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yachtorion

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I've bought some 2-pack fibreglass epoxy primer from TA Paints / Black Country Paints (I think they're actually the same company) on eBay. However what arrived was 2-pack epoxy Zinc Phosphate High Build primer. I've checked with them and this is the same material, they put the Zinc Phosphate in to avoid making two different epoxy paints. I'm wanting to use the epoxy as a waterproof barrier over some GRP which I had to sand so much that I wore through the gel in places.

Is this paint going to be suitable or does having the ZP in there make it less suitable some how?
 
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I cannot give you a definitive answer but I suspect it will be perfectly OK. It is quite common to apply more than one coat of high build primer, in which case all coats after the first would be on top of epoxy, not metal. If there was a problem it would be necessary to use two different paints, which is not the case. The paint specification used for the offshore platforms I worked on called for five or six coats of high build primer.
 
fergie_mac66 said:
you have ordered a2 pack and got a 1pack ?
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No sorry - it is still a 2pack epoxy.. I've clarified my post. I just didn't expect it to contain Zinc Sulphate and I'm wondering if having a reactive, soluble and porous substance like that in the paint will make it less suitable for my purpose...
 
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Have you already rolled some neat epoxy over the area where you rubbed through the gel coat? That would be the normal thing to do before applying the primer and paint.
 
Tranona said:
Have you already rolled some neat epoxy over the area where you rubbed through the gel coat? That would be the normal thing to do before applying the primer and paint.
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No but I can do... normal low vis resin... bung some pigment in? I was kind of hoping that the epoxy primer would fulfil that purpose to be honest, ala gelshield.
 
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Yes, you need to seal the bare GRP just as it was originally sealed with gel - but better of course with epoxy.
 
yachtailsa said:
No sorry - it is still a 2pack epoxy.. I've clarified my post. I just didn't expect it to contain Zinc Sulphate and I'm wondering if having a reactive, soluble and porous substance like that in the paint will make it less suitable for my purpose...
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Zinc phosphate or zinc sulphate?

It should not present a problem having zinc phosphate in it.
But ALL paints are porous to some degree. Thickness is what makes them less porous, (other than insertions like glass flake, mica flake etc), so if waterproofing is the game, then multiple coats required.
 
Zinc rich primer is not really necessary on GRP. The zinc phosphate is for corrosion protection. I'd use flowcoat which is more abrasion resistant than paint.
 
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Yes I do mean phosphate rather than sulphate. No wonder I failed a-level chemistry.

I think I'll probably put the primer in the cupboard for later use and mix up some pigmented epoxy resin and roll that on. It's just to make it weather tight for now before I stick the new window over the top of part of the affected area - once the interior is done I'm going to kiwi-grip the entire deck anyway.

Thanks all.
 
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