How to protect rusting bilge keels

K

kgwanchos

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Hi there Karl of Greylag a 24 ft trident here. A very happy new year to you all. My
first question of the year concerns the bilge keels. Greylags are
flaking with rust rather alarmingly and I think its time for action. It has been
recommended that I get rid of all loose rust and paint with G4 Damp
Seal here is link.....
http://www.cfsnet.co.uk/acatalog/G4_POND___DAMP_SEAL.html

3 coats then antifoul over that. Could also G4 then Gel shield as I
have a fair bit of that left from last year. Anyone have any ideas on
this or alternative suggestions ?

Many thanks
 
Use an angle grinder/sanding sheets to get back to bare metal - ususal precautions apply.

Coat with 5 coats of Primacon

Antifoul

Should do the job,.
 
Fin keels rust too! 9 months ago I took the rusty bits back to shiny with an angle grinder/flap wheel, used a rust converter (Vactan) then two coats of underwater primer (they used to call it keel primer) then 3 coats of antifoul. Came out of the water last week and has held up very well - just a few small patches to do which I must have missed last year. Otherwise jobs a goodun.
 
G'day karlos and welcome to the YBW forums with your first posting.

Cast Iron is porous and full of imperfections, sadly a grinder will only force contamination and rust further into the tiny holes as will any circular tool.

Also note; Cast iron will flash rust, rust will start to form only minutes after you get back to white metal, so some form of protection needs to be applied as soon as possible.

Dry grit blasting to class 2.5 (That's all one colour with no shadows) has proven to be one of the more effective treatments.

Coating with an epoxy resin will help keep the air and moisture out and can be applied wet on tacky to avoid sanding between coats.

We did a cast iron keel as above over 8 years ago and no sign of rust apart from a small area under the keel damaged by a grounding last year.

We also applied a coat of the same paint used on steel pylons in harbours and marinas before anti fouling, it's about 4 mm thick.

I hope this helps.

Avagoodweekend......
 
Good advice from Oldsaltoz, as usual. This is pretty much exactly what I did about 10 years ago, the boat has been almost permanenlty afloat since then, two winters ashore only. The epoxy has finally broken down last season, mainly because the coal tar epoxy that I applied over the initial epoxy has become extremely brittle and flakes off very easily.

Incidentally, 'proper' coal tar epoxy is no longer available for health reasons. There is stuff around that is still called that but it is but a shadow of its former self.

Grit blasting is not always easy to arrange, dependent upon where you are. If you fill in your Biog it gives us some idea of how to advise. What we did when I did mine was to get together a group of club members with boats at the same yard, saves money and organising.

Using any single part paint, such as polyurethane or Primocon, is always going to be second best. If you angle grind and paint one of them on you will do it again in three, four or five years. Chlorinated rubber paints are pretty good but nothing compares with good preparation and epoxy.

My keel is about to be done again in a couple of weeks, I have paid extra to have the boat hanging in slings for the duration, to ensure that the bottom of it gets the treatment as well. I will then fair the keel with epoxy plus filler, couple more coats of epoxy and then Coppercoat.
 
I've no doubt all they've said is true, but the only way we stopped rust spots on an iron fin (Sadler) was wire-brushing the muck off and painting with Hammerite. After a couple of years there was almost no rust left. Cover with Primocon & A/F of course. Lazy but effective.
 
In 2002 when I lived in France I had my Etap keel removed, sand/grit blasted and galvanised. I then had it painted with Epoxy paint. When it came out of the water in November the keel looked fine. I know removal can be difficult but if you need to change the keel bolts it may be worth doing.
Allan
 
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