Rusty Keel

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julianmingham

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I’ve some rust spots on the keel of my Westerly Oceanlord. Boat is coppercoated.
Plan is to grind the spots back to bare metal, then Primocon then Coppercoat.
My questions are:
a) should I put the Primocon on just the ground out rust spots, or all over the keel ?
b) should I put the Coppercoat on just the ground out rust spots, or all over the keel ?
 
Not sure Primocon is suitable for Coppercoat. When I did similar patches I use epoxy supplied by AMC. TBH though not easy to get patches to stick to ground out rusty cast iron and after 2 goes, had it blasted and started again.
 
julianmingham said:
I’ve some rust spots on the keel of my Westerly Oceanlord. Boat is coppercoated.
Plan is to grind the spots back to bare metal, then Primocon then Coppercoat.
My questions are:
a) should I put the Primocon on just the ground out rust spots, or all over the keel ?
b) should I put the Coppercoat on just the ground out rust spots, or all over the keel ?
Click to expand...
AMC sell a patch-up kit for small repairs. It contains everything necessary. I used one after sailing over a submerged large pot marker, gouging a deep scar in my keel. It has worked well, no different from the original coating.
 
I took my Oceanlord keel right back to bright metal. Took days, anyway iirc after several Vactan coats then several coats of Primocon and 2 antifouls, it lasted 3 months before rust blew through again. Primocon is not the stuff to use!
 
Cornishwesterly said:
I took my Oceanlord keel right back to bright metal. Took days, anyway iirc after several Vactan coats then several coats of Primocon and 2 antifouls, it lasted 3 months before rust blew through again. Primocon is not the stuff to use!
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Indeed - it's a tie coat primer with reasonably good water resistance, not a primer to protect bare metal from immersion. (Zinc phosphate epoxy for this - e.g. Penguard Express ZP)
 
vyv_cox said:
AMC sell a patch-up kit for small repairs. It contains everything necessary. I used one after sailing over a submerged large pot marker, gouging a deep scar in my keel. It has worked well, no different from the original coating.
Click to expand...
Thanks, can you please let me know the contact details for AMC ? (I’m in Portugal so supply may be an issue)
 
When I did the original coppercoat AMC supplied the primer. - It failed- When I cut back the coppercoat to re prime the rust spots I asked AMC for more primer & they said that they no longer supplied it . They suggested I sourced an epoxy primer. I did this & used the coppercoat touch up kit. However one cannot really get a smooth finish. So i ended up a couple of years later applying a full coat to the keel over the keel. I have done that twice & now have a thick layer with rust still a problem.
So because I have been applying normal antifoul to the bottom 18 inches of the keel due to it settling in the marina mud I am going to antifoul the entire keel. I notice that there is no rust showing through the previously antifouled areas. I also find that the minimum 2.5 litres of primer is expensive for a short shelf life.
I find that it is easy to antifoul a keel but not the hull. I will be using Shogun33 . In 2 years time the boat will be totally re coppercoated & i will start again with a shot blasted keel & a newly coppercoated hull.
It does not work properly, but better than grovelling under the boat applying antifoul. With coppercoat I can just have it slipped mid season & washed. I also layup all winter. Once applied a mid season jet wash is no more expensive than antifoul paint.
 
I'm just cleaning all the rust off my keel, Moody 33, it hasn't been done for several years and was very 'bubbly' - so I've cleaned it back to bare metal with a Tercoo Blaster, coated with Fertan(a rust converter) then will be coated with 2 coats of Primocon then antifoul. Will Primocon be OK or should I use something different?
 
PetiteFleur said:
I'm just cleaning all the rust off my keel, Moody 33, it hasn't been done for several years and was very 'bubbly' - so I've cleaned it back to bare metal with a Tercoo Blaster, coated with Fertan(a rust converter) then will be coated with 2 coats of Primocon then antifoul. Will Primocon be OK or should I use something different?
Click to expand...

I do the same but with 4 coats of Primocon.
 
It's worth bearing in mind that it can be VERY difficult to achieve a long-lasting result on a cast iron keel unless the original casting is of a very high quality indeed. Cast iron often has inclusions and bubbles, either of which can cause the adhesion of almost any paint system to break down eventually. My own keel is a poor casting, with one side badly pitted and full of inclusions - grit-blasting left a surface like the craters of the moon, which had to be faired using thickened epoxy. The Coppercoat lasted 7 years, with an increasing amount of flaking and rust showing through, but last winter I opted to have it antifouled with conventional antifoul. The hull is perfectly fine, and the Coppercoat is still performing well.

Any other means of preparation of the keel would perhaps have left a smoother finish that appeared to be OK, but which would have left a surface that was a smear of metal over slag inclusions. Such inclusions would have led to an even quicker breakdown of the Coppercoat.

AMC acknowledge that Coppercoat on a cast iron keel may not be as long-lasting as on GRP or a fabricated keel; I probably did fairly well to get 7 years out of it. But the only reason I achieved that was because the keel was grit-blasted by a good operator, who recognized that it was necessary to remove as much of the slag inclusions as possible. Grinding is much less effective.
 
AntarcticPilot said:
It's worth bearing in mind that it can be VERY difficult to achieve a long-lasting result on a cast iron keel unless the original casting is of a very high quality indeed. Cast iron often has inclusions and bubbles, either of which can cause the adhesion of almost any paint system to break down eventually. My own keel is a poor casting, with one side badly pitted and full of inclusions - grit-blasting left a surface like the craters of the moon, which had to be faired using thickened epoxy. The Coppercoat lasted 7 years, with an increasing amount of flaking and rust showing through, but last winter I opted to have it antifouled with conventional antifoul. The hull is perfectly fine, and the Coppercoat is still performing well.

Any other means of preparation of the keel would perhaps have left a smoother finish that appeared to be OK, but which would have left a surface that was a smear of metal over slag inclusions. Such inclusions would have led to an even quicker breakdown of the Coppercoat.

AMC acknowledge that Coppercoat on a cast iron keel may not be as long-lasting as on GRP or a fabricated keel; I probably did fairly well to get 7 years out of it. But the only reason I achieved that was because the keel was grit-blasted by a good operator, who recognized that it was necessary to remove as much of the slag inclusions as possible. Grinding is much less effective.
Click to expand...
My keel is much the same as yours, cast on its side. First time it was abraded and Coppercoated was in The Netherlands. Primed using clear epoxy about 5 coats. It lasted about 7 years and failed badly after a winter afloat in Corsica, when rust got beneath it and blew much of it off. It was then grit blasted, faired and recoated, also with clear epoxy primer, in Greece in 2007. When last seen in 2019 it was just about surviving, a few rust pits showing.
 
PetiteFleur said:
I'm just cleaning all the rust off my keel, Moody 33, it hasn't been done for several years and was very 'bubbly' - so I've cleaned it back to bare metal with a Tercoo Blaster, coated with Fertan(a rust converter) then will be coated with 2 coats of Primocon then antifoul. Will Primocon be OK or should I use something different?
Click to expand...

I used Fertan on some patches and filled a few small casting holes with car body filler. Used Jotun Vinyguard rather than Primocon and it's been fine for a few years.
 
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