Epoxy as primer?

[Porthandbuoy]

Ladybird was professionally epoxied back in the '80s. This winter I intend to remove all the old anti-fouling and do a number of below the waterline jobs; like remove a redundant seacock and echo-sounder fairing block.

It occured to me that I could give her another coat or two of epoxy before I anti-foul her in the spring. Cost isn't the issue as I have about 20 litres of West epoxy in a drum in my workshop

What does the panel think? Will it stick or come off in sheets? Will it give me additional protection against the pox? Or should I simply put the epoxy on the For Sale forum

 

[Cloven]

Not going to comment on adding new epoxy over old epoxy - others will know better than I. However, I do know from experience that once the epoxy is fully cured you cannoy use the epoxy as a primer, you MUST use an antifoul primer before coating with antifoul, otherwise, the antifoul will fall off - it happened to me on a previous boat.

When I prepared my present boat from new, the advice I had was to use a coat of hard antifoul over the not fully cured final coat of epoxy and then use self-eroding antifoul. I must say after 6 years, it seemed to have worked a treat.

Hope this helps

 

[Chris_Robb]

Ladybird was professionally epoxied back in the '80s. This winter I intend to remove all the old anti-fouling and do a number of below the waterline jobs; like remove a redundant seacock and echo-sounder fairing block.

It occured to me that I could give her another coat or two of epoxy before I anti-foul her in the spring. Cost isn't the issue as I have about 20 litres of West epoxy in a drum in my workshop

What does the panel think? Will it stick or come off in sheets? Will it give me additional protection against the pox? Or should I simply put the epoxy on the For Sale forum

Epoxy will not stick to cured epoxy, unless a mechanical bond is made - abrading. Unless you doubt the integrity of the initial coats, I would not touch it. Take note of the priming required for new antifouling.

 

[Gelmaster]

epoxy has its own set of rules when it comes to chemical and mechanical bonding!
Basically, epoxy is happy to bond to polyester "cured" resin with a chemical bond, but i would always key it in with sanding back with 40 or 80 grit paper first to make sure!

There is a specific epoxy cleaning solvent available also.
Polyester resin, on the other hand, doesnt like bonding to epoxy!

If your exhisting coats arent too bad, then dont waste your time!

If its not broke...etc

PS...that drum in the garage, resin has a shelf life. If it now resembles wallpaper paste, i would be very reluctant to use it!

 

[Porthandbuoy]

There is a specific epoxy cleaning solvent available also.

Didn't know that.

If your exhisting coats arent too bad, then dont waste your time!

There's several coats, different shades, different brands. I want to get back to the hull and check for blisters anyway.

If its not broke...etc

Couldn't agree more, but like I said, redundant skin fittings need to go.

PS...that drum in the garage, resin has a shelf life. If it now resembles wallpaper paste, i would be very reluctant to use it!

I knew the hardener had a relatively short shelf-life but thought the resin could be measured in years if kept out of the light. It was okay last time I checked; crystal clear and syrupy. Thanks for the advice though.

 

[oldsaltoz]

Didn't know that.


There's several coats, different shades, different brands. I want to get back to the hull and check for blisters anyway.


Couldn't agree more, but like I said, redundant skin fittings need to go.


I knew the hardener had a relatively short shelf-life but thought the resin could be measured in years if kept out of the light. It was okay last time I checked; crystal clear and syrupy. Thanks for the advice though.

Sanding back to the older epoxy coat for an inspection will be an expensive exercise because it will remove the original epoxy primer between antifoul and epoxy coat.

After the new coat of epoxy is cured it must be abraded and coated with a high build epoxy primer, this must be left to cure and abraded prior to antifouling again.

It's a good idea to apply another mist coat of high build epoxy primer just before the new antifoul and apply the first coat of antifoul over the wet primer, this will mix with primer and give you an indication of the proximity to primer when next sanding back, thus avoiding contact with the epoxy coat.

Any blisters will be visible 'before' you reach the epoxy layer, so why remove it or risk damaging it? and adding the cost of re priming.

 

[Chris_Robb]

Sanding back to the older epoxy coat for an inspection will be an expensive exercise because it will remove the original epoxy primer between antifoul and epoxy coat.

After the new coat of epoxy is cured it must be abraded and coated with a high build epoxy primer, this must be left to cure and abraded prior to antifouling again.

It's a good idea to apply another mist coat of high build epoxy primer just before the new antifoul and apply the first coat of antifoul over the wet primer, this will mix with primer and give you an indication of the proximity to primer when next sanding back, thus avoiding contact with the epoxy coat.

Any blisters will be visible 'before' you reach the epoxy layer, so why remove it or risk damaging it? and adding the cost of re priming.

I have to do some small repairs to the bottom of the rudder - due to hitting something in the French Canals last year. The rudder was treated for osmosis with peeling and epoxy coat, which has broken off in a number of places on the leading edge. with mechanical abrasion only, can new epoxy be applied ok?

 

[Gelmaster]

Tricky! If the damage is fairly minor, and there is an exhisting epoxy coating, then definately stay with an epoxy based repair!
There are some excellent polyester based repair fillers on the market,
containing fine fibres of fibreglass..."Fibrol", but unfortunately wont take to anything epoxy based. dont want to get all techy...but its all to do with the polymers in the material.
So yes....an epoxy repair is called for, but key it in well with sandpaper first then clean with either acetone or epoxy solvent.
Even natural sweat and oils from your hands will reduce the bond, so try not to touch before applying the epoxy filler!

 

[Gelmaster]

Still think it would be best left alone.
It sounds great, 20 litres of epoxy just sat there saying..Use me!, I am the answer to all your dreams!....
You say there are several coats of G** knows what!
If there are any problematic blisters present, you will probably notice them on cleaning back anyway!
So, i would simply clean back, and re-antifoul!

To apply some fresh coats of epoxy would be labour intensive on the prep and ideally you would have to invest in an epoxy solvent and primer!
Expense for no reason maybe !!

 

[oldsaltoz]

I have to do some small repairs to the bottom of the rudder - due to hitting something in the French Canals last year. The rudder was treated for osmosis with peeling and epoxy coat, which has broken off in a number of places on the leading edge. with mechanical abrasion only, can new epoxy be applied ok?

First you MUST ensure the core and area to be repaired are very dry.

You can mix a small batch of epoxy resin, paint a little along the damaged edge then add Micro Fibres to the mix, stiff enough to stand in peaks like peanut butter, apply this to the edge of the rudder to build up any low areas.

Allow to cure and sand to shape then apply at least 3 coats of renin wet on tacky to avoid sanding between coats.

Good luck.

 

[Porthandbuoy]

Still think it would be best left alone.
It sounds great, 20 litres of epoxy just sat there saying..Use me!, I am the answer to all your dreams!....
You say there are several coats of G** knows what!
If there are any problematic blisters present, you will probably notice them on cleaning back anyway!
So, i would simply clean back, and re-antifoul!

To apply some fresh coats of epoxy would be labour intensive on the prep and ideally you would have to invest in an epoxy solvent and primer!
Expense for no reason maybe !!

You've convinced me. I'll clean back to a smooth substrate, probably prime as I don't know what's on there, and anti-foul.
I'll mix a test batch of my epoxy and make sure it's okay for the redundant fittings repair.

Glad I asked though. Thanks

 

[ccscott49]

Still think it would be best left alone.
It sounds great, 20 litres of epoxy just sat there saying..Use me!, I am the answer to all your dreams!....
You say there are several coats of G** knows what!
If there are any problematic blisters present, you will probably notice them on cleaning back anyway!
So, i would simply clean back, and re-antifoul!

To apply some fresh coats of epoxy would be labour intensive on the prep and ideally you would have to invest in an epoxy solvent and primer!
Expense for no reason maybe !!

You might be able to answer a question for me.
I am going to blast off all my antifoul, on a wooden boat, sheathed from new with cascover, which is in excellent condition. Taking it right back to the cascover, but not damaging it. Would it be beneficial to put a coat of epoxy antifoul primer on to the cascover first, will it bond (the surface will be abraded, from the blasting). Or could I just use a west epoxy resin first, then antifoul? Seems you are saying antifoul wont bond to epoxy?

 

[Chris_Robb]

First you MUST ensure the core and area to be repaired are very dry.

You can mix a small batch of epoxy resin, paint a little along the damaged edge then add Micro Fibres to the mix, stiff enough to stand in peaks like peanut butter, apply this to the edge of the rudder to build up any low areas.

Allow to cure and sand to shape then apply at least 3 coats of renin wet on tacky to avoid sanding between coats.

Good luck.

Thanks - should hopefully be dry after 6 months out of the water in Greece. Must have hit shopping trolleys or something in the canals!

 

[vyv_cox]

Seems you are saying antifoul wont bond to epoxy?

I think someone else may have answered this further up. When I Gelshielded my hull the advice was that after five coats of the epoxy a coat of hard scrubbable antifouling should be applied within a short time, before the epoxy has cured. This acts as a primer and eroding antifoul can then be applied over it.

 

[Gelmaster]

You might be able to answer a question for me.
I am going to blast off all my antifoul, on a wooden boat, sheathed from new with cascover, which is in excellent condition. Taking it right back to the cascover, but not damaging it. Would it be beneficial to put a coat of epoxy antifoul primer on to the cascover first, will it bond (the surface will be abraded, from the blasting). Or could I just use a west epoxy resin first, then antifoul? Seems you are saying antifoul wont bond to epoxy?

Sorry, only just seen the question...

antifoul will take to epoxy, especially just before it cures (at the tacky stage)
If your cascover is in good condition, then i would be temted simply to antifoul, but use an appropriate brand A/F primer first!
Epoxy coatings always offer excellent water defence, but can be expensive.
Only use the epoxy if the cascover is in doubt!!

 

[ccscott49]

Sorry, only just seen the question...

antifoul will take to epoxy, especially just before it cures (at the tacky stage)
If your cascover is in good condition, then i would be temted simply to antifoul, but use an appropriate brand A/F primer first!
Epoxy coatings always offer excellent water defence, but can be expensive.
Only use the epoxy if the cascover is in doubt!!

Thanks for that, I'll do exactly that, antifoul primer and then eroding antifoul, 40 litres of it!!