Antifoul - thickness and peeling

[Sailfree]

I thought antifoul was self eroding and you just power washed it and scoured it with a green scourer and overcoat with extra coat of antifoul each year.

Last year I had small areas breaking off and I sanded down these areas. I then also had some other apparently sound areas peel off when overcoating with new antifoul. Talking about say on average 25mm round patches.

I think its adhesion problems possibly due to not scouring original surface enough or possibly not properly mixing Antifoul thoroughly.

This year I have started by using a carbide scraper on any loose areas and then sanding down using a Metabo 150mm Dual Action sander until I get a tapered edge. Finding some areas the layer doesn't so much as grind off but chips off again leaving an edge. On underside its just thin layers but towards side I am surprised by the total thickness.

Usually get through some 5ltrs of International Micron Extra on a 43' boat.

Can you put antifoul on too thick?

Can the layers build up too much?

Do you just pressure wash and overcoat or do you scour surface or even rub the surface down a bit?

 

[Cloven]

Common problem. I jet wash and then scrape off any obvious loose stuff. Then I put a little antifoul primer on those areas before doing the full antifoul treatment. I find it worse if the boat has been ashore for a long period, ie over the winter.

 

[Sailfree]

antifoul primer - am I missing something!!

 

[charles_reed]

I only started antifouling my boat after 10 years (it came with Scott Baders Coppercoat in 1990). I got so fed up with the biannual necessity of wet&dry rub-down.
I soon found that two coats was overkill and have always used a single coat since the 5 coats of gelshield in Malta in 2007. Occasionally wear through the eroding antifoul to the different colour 1st coat of hard - just need to put an extra coat on those areas of extra wear.
My boat is probably on the move more than most (last year 1400nm), but 2.5litres of antifoul is OK for a single coat and is easy on the pocket. The only time the waterline got dirty was 4 days in Kos Old Port port and that was oil scum.

So loose antifouling and lack of adhesion is, IMHO, is down to unneccesarily conspicuous consumption of antifouling.

 

[Sailfree]

Charles

Thanks

I am putting a red coat over the original black this time so I can better judge the self erosion.

Every day is a new lesson!!

 

[Cloven]

antifoul primer - am I missing something!!

Antifoul primer is recommended unless you are overcoating like with like ie. same make/type of antifoul aa peeviously used. It creates a key between the old and new

 

[William_H]

The build up of antifouling is a common problem. After some years most people end up with a major project of scraping of a/f or getting it sand balsted off at great expense.
It really becomes obvious when some flakes off to give that horrible sharp edge of roughness.
I don't have any suggestions for for my UK friends except to use as little a/f as possible.
My own approach in really bad fouling conditions. (warm water and lots of sun, 32degrees south) Is to paint at the start of the season. Within 6 or 8 weeks I am scrubbing in water at least once per week to keep it clean. By now with the season end in sight I am scrubbing madly with wet and dry sand paper trying to remove as much a/f as possible. Access to all the hull is difficult on the trailer when it is out. Meanwhile where the a/f has gone completely fine strands of weed are growing like a centimetre long in 2 days. Fortunately I enjoy the swimming/diving. good luck olewill

 

[GrahamM376]

This year I have started by using a carbide scraper on any loose areas and then sanding down using a Metabo 150mm Dual Action sander until I get a tapered edge. Finding some areas the layer doesn't so much as grind off but chips off again leaving an edge. On underside its just thin layers but towards side I am surprised by the total thickness.

Usually get through some 5ltrs of International Micron Extra on a 43' boat.

Can you put antifoul on too thick?

Can the layers build up too much?

Do you just pressure wash and overcoat or do you scour surface or even rub the surface down a bit?

Sounds like it may be time to give it a good scrape all over, pain of a job which I did a few years ago as mine was exactly as you describe. I use 5L on 38ft boat, one coat all over then second around the waterline, rudder, skeg, prop area & keel leading edge. Since I scraped it no flaking on later coats and where it erodes unevenly I feather the edges. After power wash I go all over with a green kitchen scourer.

 

[Sailfree]

Sounds like it may be time to give it a good scrape all over, pain of a job which I did a few years ago as mine was exactly as you describe. I use 5L on 38ft boat, one coat all over then second around the waterline, rudder, skeg, prop area & keel leading edge. Since I scraped it no flaking on later coats and where it erodes unevenly I feather the edges. After power wash I go all over with a green kitchen scourer.

Thanks it appears that after 10yrs I am no different to anyone else. I think I use nearer to 6-7ltrs of Micron Extra each year. Started by scraping off the obvious loose areas and then sanding down until I get a nice feathered edge with a DA sander. Done Rudder and 25% of hull today but reaching up all the time is hard work for us normal desk jockeys.

May have some muscles by the end of this exercise!!

 

[Robin]

Thanks it appears that after 10yrs I am no different to anyone else. I think I use nearer to 6-7ltrs of Micron Extra each year. Started by scraping off the obvious loose areas and then sanding down until I get a nice feathered edge with a DA sander. Done Rudder and 25% of hull today but reaching up all the time is hard work for us normal desk jockeys.

May have some muscles by the end of this exercise!!

Get one of the dry wall sander things on a pole and fit it with the open mesh sanding stuff that doesn't clog. Use loads of water and keep it flowing and you get a nice slurry going that speeds the process. We use to do our 41 footer in about 2 hours, SWMBO on the hose me on the sander. Wash it off well to get all the dust off and apply more antifoul. We used Micron Extra in white and always applied 2 full coats every year. NOW in the USA, we are following local custom of staying afloat and having monthly cleans by a diver. WE are in the tropics so fouling is otherwise rapid. We still use Micron Extra now in black, but the USA version.

 

[Fantasie 19]

Do you just pressure wash and overcoat or do you scour surface or even rub the surface down a bit?

pressure wash and overcoat..

 

[jwilson]

Every year despite first pressure-wahing and then rubbing the old AF down with sanding-mesh-on-a-pole I find that on rolling on a single coat of fresh AF in small areas the old layers right back to the gelcoat come off. When you find this you often find larger surrounding areas with poor adhesion right back to the gelcoat. AF layers themselves stick together fine: it comes off all-or-nothing.

I'm sure that the problem is that when the boat was new 10 years ago the hull did not have all the mould wax fully removed. After 10 years I now have a still very reasonable for cruising but not totally racing smooth finish. If AF comes off back to the gelcoat at the pressure-wash stage the area gets a wet wet-and-dry rub down and then a coat of primer. Once that's done that few inches seems fine thereafter. Not much you can do if you find new flaky patches at rolling on new AF time other than cover it up.

One day I'll get it all soda-blasted off and start again, but a few years away yet.

 

[rogerthebodger]

pressure wash and overcoat..

Thats what I do, pressure wash one low tide overcoat next low tide. I do an in water scrub every 3 to 4 months

I anti foul every second year and seems to last but does need more scrubs towards the end of the second year.

 

[Easticks28]

Every year despite first pressure-wahing and then rubbing the old AF down with sanding-mesh-on-a-pole I find that on rolling on a single coat of fresh AF in small areas the old layers right back to the gelcoat come off. When you find this you often find larger surrounding areas with poor adhesion right back to the gelcoat. AF layers themselves stick together fine: it comes off all-or-nothing.

I'm sure that the problem is that when the boat was new 10 years ago the hull did not have all the mould wax fully removed. After 10 years I now have a still very reasonable for cruising but not totally racing smooth finish. If AF comes off back to the gelcoat at the pressure-wash stage the area gets a wet wet-and-dry rub down and then a coat of primer. Once that's done that few inches seems fine thereafter. Not much you can do if you find new flaky patches at rolling on new AF time other than cover it up.

One day I'll get it all soda-blasted off and start again, but a few years away yet.

+1 for a pole sander! Did my 28' long keel boat in about 35 minutes using 80 grit paper.The boat was dry 3 months after haul out. I will try mesh next year.

 

[Sailfree]

Jwilson,

Seems like many have similar problems.

I have very few bits coming off down to gel coat but there are a few and probably due to poor cleaning of mould wax.

When I bought boat it had a leaking bow thruster due to Jeanneau South coast distributor deleting it from order and getting Bob the builder to install it after delivery! They suggested that I leave it until next years lift out and they would fix leak and antifoul boat FOC. I was assured they would prep hull properly. I arrived near the end to find they were antifouling straight over the pressure wash. With all the commissioning problems I was silly not to expect this and should have monitored the work better but my own work time commitments got in the way.

Commissioning antifoul was blue and subsequent years are black. Its the adhesion to the blue antifoul that seems to be the problem. Both blue and black was Micron extra.

Will sand down all loose areas this year and see how it is next year.