Epoxy question

  • We are currently upgrading MFK. thanks! -neo
A

apisto

Gambusia
MFK Member
Jul 7, 2009
194
2
16
Cork, Ireland
Hi all,
I have sealed my plywood tank with two tone epoxy and added some black pigment. The inside of the tank was balck on all shiny. I filled the tank the other day and now the epoxy is matt. It almost looks like it is covered in limescale which it isn't. My tapwater has a hardness of only 2 GH and I can't really wipe it off. Any idea what this might be? I used five layers of epoxy, mixed resin and hardner as per instructions and let the whole thing cure for more than a week. BTW the tank does not leak
Any suggestions welcome
 
not really. It's only on the back panel and not on the side panels. Once it doesn't have an impact on stability I don't care since it looks black once the water covers it. I will drain it tonight and see if there's any change
 
It is a common reaction with some epoxy resins called "amine blush" It is a greasy residue that forms on the surface. It can happen with cheap epoxies even in dry conditions but it is usually from curing in cold or damp conditions. Put simply, it is a reaction between amine hardeners,moisture and carbon dioxide.This is why the use of quality marine epoxy resins are best. I like Bote Cote Epoxy as its hardeners are free of this side reaction.

To get rid of it, use a scourer with an ammonia based cleaner. Rinse with water, dry and resand before applying another coat under the correct conditions. It is also good practise to have both part A and B pre-warmed before mixing. Many use a light box for this but any means of raising the temp so it is luke warm and not cold will help greatly.
 
thanks for that bit of information. Does the amine blush have any negative impact on the waterproofing or stabilty of the epoxy? The epoxy was applied in warm weather and inside so I don't think that temperature or dampness was the issue. I also used the correct amounts of epoxy and hardener. The label specifically mentions for use in aquaria. Might the pigment be the cause?
 
Unfortunately warm weather does not mean low humidity. Humidity is where the moisture comes from. Amine blush is usually just surface orientated. If it is deep, it is often poor mixing etc. That being said, assuming that conditions were right from temp to mix ratio, it comes down to 3 things IMO. The % of pigment used (too much can stop the cure process but this will be the whole layer and not just on the surface.), the pigment itself(comparability) or the product itself.
As for waterproof? That is hard to answer without seeing it first hand. Personally, I would sand it and re-coat it in dry warm conditions. If you still have problems and you are positive everything was done right and in the correct conditions, I would be quetioning the particular product.
 
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