Antifouling over old epoxy

G

Gypsyjoss

Well-Known Member
Joined
29 May 2008
Messages
268
Location
Midlands -a long way from the sea!
Visit site
2 questions and one is an oops! question.

1. I scraped 10 years of antifouling down to the the epoxy coating (4 layers) off my S32 last July out in Greece but had no time to do anything else. Will exposure to UV over a period of 9 months have done any damage?

2. Can I antifoul directly onto the epoxy surface, which looked quite glossy? Should it be lightly sanded first or an etching primer applied? I tend to use cheap Greek self-cleaning paint.

Cheers!
 
Gypsyjoss said:
2 questions and one is an oops! question.

1. I scraped 10 years of antifouling down to the the epoxy coating (4 layers) off my S32 last July out in Greece but had no time to do anything else. Will exposure to UV over a period of 9 months have done any damage?

2. Can I antifoul directly onto the epoxy surface, which looked quite glossy? Should it be lightly sanded first or an etching primer applied? I tend to use cheap Greek self-cleaning paint.

Cheers!
Click to expand...

1. No

2. You must coat the old epoxy layer with an antifoul primer of the new antifoul will not stick - does not need to be an etch primer.
 
Err, you need to check that the primer is suitable over an epoxy, most are not.

As I keep saying on here " Epoxy will stick to almost anything dry, but almost nothing will stick to Epoxy"

You may need to add a coat or 3 of an Epoxy High Build Primer first to ensure you shiny new anti fouling does not fall off in the first week.

Good luck and fair winds. :)
 
Lazy Kipper said:
If gelcoat is epoxy, how does ordinary antifoul primer stick so well to it?
Click to expand...

99.9% of all gelcoat applications are not epoxy based.

The very few that have been coated with an epoxy based gelcoat must be primed with a high build epoxy primer first. As already stated "almost nothing sticks to an epoxy based resin".

Good luck and fair winds. :)
 
oldsaltoz said:
... coated with an epoxy based gelcoat must be primed with a high build epoxy primer first. As already stated "almost nothing sticks to an epoxy based resin".
Click to expand...
"Almost nothing" ? Not so sure about it, meself... and no reason for 'high built', just normal primer, if necessary.
"High Built" primer is in reality a paint with filler added, for filling/sanding. Some fillers can soak with water and should not be used below water - better to check. Awlgrip high built is an example.

Just check info on the antifouling you want to use - there should be said, on the can, what surface it works on or what primer to use. If you're lucky enough to find any info at all...

Many antifouling paints are specially made to keep on epoxy. Well, some are made of epoxy actually, even the soft ones. Most ships are covered with epoxy systems anyway, also there are special epoxy 'tie-coats' for antifoulings, or many antifouling systems use epoxy primers to get adherence... Interlux or International use "Interprotect" - it's just clear epoxy primer; guess this will stick to epoxy... ;)

Real problem for boat owner is to get proper information on the stuff he can buy in the "marine" store...
But we got to get some idea somehow :confused:
Sadly, producers hide the precise info on their products from consumers lately. I cannot advise to buy the one who provides proper info as just got it hard to find one, and I'm in the same situation with epoxy paints on bottom. Which were painted with antifoul without any priming, btw.


Frankly it would be normal to sand a bit to roughen and slap antifoul on; and normally the paint will stick. But when they don't say what paint their paint is, other that "Best Quality Modern Formulation For Greatest Result" ;) we get into a lottery...
 
Last edited:
Rossynant said:
"Almost nothing" ? Not so sure about it, meself... and no reason for 'high built', just normal primer, if necessary.
"High Built" primer is in reality a paint with filler added, for filling/sanding. Some fillers can soak with water and should not be used below water - better to check. Awlgrip high built is an example.

The prime reason for using a high build primer is avoid damaging the epoxy when cleaning off old anti foul.

I always add a thin layer of primer after the main coat has cured and then a thin layer of the antifouling paint onto the uncured surface, let it all cure the finish appliying the antifoul.

This means the next time I sand it back I will see the mixed promer and antifoul before I get to the epoxy layer.

Just check info on the antifouling you want to use - there should be said, on the can, what surface it works on or what primer to use. If you're lucky enough to find any info at all...

Many antifouling paints are specially made to keep on epoxy. Most ships are covered with epoxy systems anyway, also there are special epoxy 'tie-coats' for antifoulings, or many antifouling systems use epoxy primers to get adherence... Interlux or International use "Interprotect" - it's just clear epoxy primer; guess this will stick to epoxy... ;)

Real problem for boat owner is to get proper information on the stuff he can buy in the "marine" store...
But we got to get some idea somehow :confused:
Sadly, producers hide the precise info on their products from consumers lately. I cannot advise to buy the one who provides proper info as just got it hard to find one, and I'm in the same situation with epoxy paints on bottom. Which were painted with antifoul without any priming, btw.


Frankly it would be normal to sand a bit to roughen and slap antifoul on; and normally the paint will stick. But when they don't say what paint their paint is, other that "Best Quality Modern Formulation For Greatest Result" ;) we get into a lottery...
Click to expand...

Good luck and fair winds. :)
 
oldsaltoz said:
The prime reason for using a high build primer is avoid damaging the epoxy when cleaning off old anti foul.
Good luck and fair winds. :)
Click to expand...
Well, I'm not saying anything against protecting the existing epoxy, advised it myself earlier - but the question here was " Can I antifoul directly onto the epoxy surface, which looked quite glossy? Should it be lightly sanded first or an etching primer applied? I tend to use cheap Greek self-cleaning paint."
My opinion: Yes, you can, at least some antifoulings can be applied directly onto this old epoxy, and with ablative paint it's not such a great problem with sanding it off later on. Just hard for me to say which brands, but certainly the "Must be" and "nothing sticks to epoxy" is exaggeration.
With Hi-build primers there is some problem, in fact - who can be sure they will not start to fall of after some 5-10 years? Once those fail, being under paint system, the owner is left with hull to strip back to GRP... Have seen this to happen.

As I said - found it hard to get info on such things in English language, so I cannot speak for products available in UK.
For me it's simpler a bit - you know, hiding details of chemicals from customer is in fact illegal, at least hereabout, but also under EU law lately (directive from 2006 iirc) so I have descriptions, only US and UK brands remain a mystery :o

As OP is in Greece and Polish paints can be found there, I'll show one example for instance, which should stick to epoxy, as this is epoxy-based paint actually :)
Some tips for application can be downloaded, in English also, from here http://www.shop.bootslacke-nord.de/tech-datenblaetter/category/1-sea-line.html - not much to say about as the paint really can be just painted on, nothing more to say :o

But in Polish whole instructions are given, such as http://sea-line.eu/file/podrecznik sealine 2013.pdf
and chemical characteristic of paint, as legally should be provided - so all ingredients are shown http://sea-line.eu/file/kch/antifouling antyporostowa.pdf
Sorry, but for UK market only such is customarily required (don't ask why, beats me...) - 1-page "characteristic", looks this way http://sea-line.eu/file/kta2/antifouling selfpolishing.pdf

One tip - in case there is no info in English, try German :D Germans still like to be precise.
 
Last edited:
I have applied International Micron directly on an epoxy coating (Gel shield I think) with no problems at all in the last 6 years, just make sure the surface has been abraded, wash down and paint it on. In my experience a primer/undercoat is not necessary apart from adding to the profit margins of the paint manufacturers.
 
Georgio said:
I have applied International Micron directly on an epoxy coating (Gel shield I think) with no problems at all in the last 6 years, just make sure the surface has been abraded, wash down and paint it on. In my experience a primer/undercoat is not necessary apart from adding to the profit margins of the paint manufacturers.
Click to expand...

I had an exactly the opposite experience. Had first boat epoxied (Gelshield) professionally. Applied antifoul next day - following day most had flaked off. Scraped rest off. Applied antifoul primer, then antifoul & no problems thereafter
 
You must log in or register to reply here.

Share this page

Top