Epoxy

[medsailor1]

Hi can anyone tell me the disadvantages and advantages of solvent epoxy and non solvent epoxy please

[lateral]

Solvent epoxy obviously penetrates and releases air better, but is weaker
And more moisture permeable.
I rarely use solvent except first coat on timber to minimise outgassing on subsequent Non solvent coats.

[medsailor1]

I need to treat a iron keel which is going to be copper coated .
Not know much about epoxy , I trying to work out best option

[Wotname]

Originally Posted by medsailor1

I need to treat a iron keel which is going to be copper coated .
Not know much about epoxy , I trying to work out best option

Then you want non solvent; also known as 100% solids epoxy.

As lateral posted, solvent epoxy is not waterproof.

Why - as the solvents evaporate while the epoxy is curing, they leave holes in the epoxy matrix which allows moisture to penetrate into the epoxy surface.

This can't occur when using non solvent epoxy which contains 100% solids.

[model 10]

[QUOTE=Wotname
This can't occur when using non solvent epoxy which contains 100% solids.




If the mix ratio is 5:1, do you have more solids than a 1:1 epoxy? I've not heard of anything better than 5:1. What does this mean?

[rbk]

Think of it like an oil and water mixture poured out on a large sheet of paper, as the water (solvent) evaporates patches of oil (solids) are left.

[medsailor1]

So the next question is , copper coat UK say ,
if A non solvent epoxy Is used , to over coat it with copper coat while still tacky ,
Can't it be left for say a week then lightly sand it to key it and then copper coat over it ?

[Thumbs Up]

You should look up "coal tar epoxy"

[Jim Cate]

Originally Posted by medsailor1

So the next question is , copper coat UK say ,
if A non solvent epoxy Is used , to over coat it with copper coat while still tacky ,
Can't it be left for say a week then lightly sand it to key it and then copper coat over it ?

..

Deviating from mfg's instructions is always risky, especially when dealing with materials used under water. If you really want to do this, don't ask us, ask the folks who make the stuff. If it then fails, you have some recourse (not much, though). If you follow our advice and it fails, well, too bad!

Jim

[er9]

Originally Posted by medsailor1

So the next question is , copper coat UK say ,
if A non solvent epoxy Is used , to over coat it with copper coat while still tacky ,
Can't it be left for say a week then lightly sand it to key it and then copper coat over it ?

probably not. If you get a coat of copper coat on before the epoxy cures i believe they bond partially at a molecular level...if you wait until the epoxy cures the best you could hope for is a mechanical bond which would be far inferior bond.

[Franziska]

Definetly not.

The reason for applying the copper coat while the epoxy underneath is still tacky is that they form a chemical bond between each other than.

In the sanding case you are suggesting you only achieve a physical bond, which is far worse than the chemical bond.

And yes tar epoxy like VC Tar is a great barrier coat used for many years.
Still check with the copper coat guys if there is anything in there which they do not like to go under copper coat.

Definetly wear proper safety gear when applying VC Tar, it's not very healthy when uncured!

Originally Posted by medsailor1

So the next question is , copper coat UK say ,
if A non solvent epoxy Is used , to over coat it with copper coat while still tacky ,
Can't it be left for say a week then lightly sand it to key it and then copper coat over it ?

[Wotname]

Originally Posted by Ecos

If the mix ratio is 5:1, do you have more solids than a 1:1 epoxy? I've not heard of anything better than 5:1. What does this mean?

The mix ratio doesn't have anything to do the percentage of solids in the epoxy.

In a solvent free epoxy, there are no solvents in either part.

So when using say a 5:1 ratio (by weight), the cured epoxy will be 6 units and if say the ratio was 2:1, then the cured epoxy will be 3 units.

[model 10]

[QUOTE=Wotname;2981205]The mix ratio doesn't have anything to do the percentage of solids in the epoxy.


What does a 5:1 ratio mean? The cheap epoxy in Rio Dulce is 1:1. West Systems I think is 5:1 and that much more expensive.

[Wotname]

These guys can explain it better than me
https://www.westsystem.com
https://www.epoxyworks.com