Primer/Coating for Cast Iron Keels in Pre. for Coppercoat

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Andrew_Trayfoot

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Evening all....

I'm looking for recommendations for what to paint the cast iron keels with once they have been 'blasted' back to bare metal before applying copper coat this winter.

The boat is a 26' Westerly Griffon.

Thanks,

Andrew
 
Jotun Vinyguard, pretty inexpensive if bought sensibly. Use a well thinned first coat. Put as many coats on as you have the patience for, the thicker the primer layer the better.
 
When I had my boat Coppercoated I was advised not to have my keels done. The yard said it wouldn't last as you can't stop cast iron from rusting long term. So I just have a keel to blitz, rust converter, prime and AF. Not a big job. Of course I envy those with keels that are Coppercoated.
 
As suggested very difficult to get existing cast iron keels clean enough to Coppercoat, but if you do try then you need them properly blasted and immediately epoxy coated following Coppercoat recommendations. You need to use a blasting company that as experience preparing for Coppercoat and probably best to also get them to do the epoxy.

Vinyguard is not suitable but is fine if you are opting for conventional antifouling.
 
My keel is Coppercoated. It was grit blasted and immediately (less than 20 minutes recommended) with West epoxy. A subsequent four coats were applied as soon as the preceding coat was dry.

Coppercoat recommend Hycote 152 or GP120, both epoxies. Do not use a non-epoxy primer beneath Coppercoat: it will not adhere.
 
When I took my keel back to the metal for treatment, I had plenty of time, because I was doing other work on the hull. Having researched what others have done and taking the advice from someone with long experience, I did the following, some of which is based on science and some on pub/forum discussions.

The yard do not allow blasting, so I took all the old paint and filler off with a tungstened tipped disk on a drill, commonly used in the canal boat world. Followed with a good abrasive disks on the angle grinder. This this was completed over some weeks, because I had other less horrid jobs that needed attention. I let the metal rust and washed the keel to remove any salt within the cast iron.

When everything was cleaned, I did a quick run over with the angle grinder with course disks, wiped it down the left it overnight to form some rust. The first stage was to apply PORs rust convertor the keel, and it went a nice black. (it does need rust to convert it does not do anything a non-rusty metal). I was not in a position to apply the next coat, so again I did no more. The rust convertor (phosphoric acid) did work and no rust appeared in the next month or so . This last point is just for interest and a comment that the PORS worked well and in deed appeared to be better that other treatments I have applied.

I so not know it the washing helped to reduce rust. A keel two boats down from sanded his rusty bubbles and applied rust converter, another brand, it looked good for two weeks the rust appeared again.

For the treatment proper, I repeated a clean back wipe down leave and applied the rust convertor. I the applied 3 coats of Reactive Resins Armourguard. A flexible rubber in epoxy, tank coating , which is designed to exclude both moisture and air ( Oxygen) from the metal. It bonds well and copes with movement and temperature change. I the filled and faired the keel and applied a further coat of Armourguard. I also applied three coats of Reactive Resins TSF (totally solvent free) as part osmosis prevention on the hull. Then finally Coppercoat.

I am confident this will last more than the 7 years that it took for the previous treatment took to begin to have rust spots and more than the time it took for me to think I should address the rust. I am confident that It will outlast the copper coat and possibly outlast me. I will be able to confirm my optimism in another 5 years, I doubt that you can wait that long for conformation.

Unfortunately Reactive Resins went bust last year but as they say " other flexible tank coatings" are available.
 
duncan99210 said:
Give Coppercoat a call and they’ll advise. I seem to recall being told to use International Interprotect, as many coats as I had time to apply, but things do change so give them a call. They’re very responsive to phone call and always have someone available to chat.
Click to expand...

+1

Ring AMC, they're very helpful indeed. For my lead keel in 2015 it was also Interprotect under the Coppercoat, and both are still there.
 
The first attempt to coppercoat my keel was as done by the yard. They shot blasted it and then filled and faired with epoxy and International epoxy (Gelshield. I think?) I had lots of rust patches within a year. The yard was In Scotland and I’d brought Serendipity back S again so it was impractical to take it back and argue for some warranty work.

After a couple of years I got fed up with the rust patches so had the keel shot blasted again. This time I built a tent or skirt of tarpaulin round the boat and put half a dozen heaters inside to raise the temperature. It takes quite a while to raise the temperature of the thermal mass of the keel, but the first coat of epoxy was applied by the shot blasting man within minutes of the keel being blasted. I then filled and faired the keel and with friends put on over seven coats of epoxy before reapplying coppercoat. Two years on there’s not a trace of rust coming through yet. Friends who have done the same have the occasional minor patch that they clean off with a flapper wheel and redo the process on the patch and cured the problem.
 
My iron keels are coppercoated. I made sure the blasting was done on a dry day and that the yard was ready to apply epoxy IMMEDIATELY the keels were blasted. It was amazing how quick rust formed on the bare iron. I was wire brushing the newly blasted keel about 1 foot ahead of the guys applying the epoxy and was getting fine rust off even though it was minutes since the blasting finished. Six layers of epoxy were applied (in alternating colours to ensure complete cover for each layer) Four years in and the keels look mint.
 
Andrew_Trayfoot said:
Evening all....

I'm looking for recommendations for what to paint the cast iron keels with once they have been 'blasted' back to bare metal before applying copper coat this winter.

The boat is a 26' Westerly Griffon.

Thanks,

Andrew
Click to expand...

Onl;y use epoxy and I would suggest a conventional non solvent one. You need to get an impermiable surface finish because without air and water, your keels cant rust. So be careful about pinholes in the epoxy coat.

I wouldnt dream of using a one pack paint like vinyl undercoats.
 
sailor211 said:
When I took my keel back to the metal for treatment, I had plenty of time, because I was doing other work on the hull. Having researched what others have done and taking the advice from someone with long experience, I did the following, some of which is based on science and some on pub/forum discussions.

The yard do not allow blasting, so I took all the old paint and filler off with a tungstened tipped disk on a drill, commonly used in the canal boat world. Followed with a good abrasive disks on the angle grinder. This this was completed over some weeks, because I had other less horrid jobs that needed attention. I let the metal rust and washed the keel to remove any salt within the cast iron.

When everything was cleaned, I did a quick run over with the angle grinder with course disks, wiped it down the left it overnight to form some rust. The first stage was to apply PORs rust convertor the keel, and it went a nice black. (it does need rust to convert it does not do anything a non-rusty metal). I was not in a position to apply the next coat, so again I did no more. The rust convertor (phosphoric acid) did work and no rust appeared in the next month or so . This last point is just for interest and a comment that the PORS worked well and in deed appeared to be better that other treatments I have applied.

I so not know it the washing helped to reduce rust. A keel two boats down from sanded his rusty bubbles and applied rust converter, another brand, it looked good for two weeks the rust appeared again.

For the treatment proper, I repeated a clean back wipe down leave and applied the rust convertor. I the applied 3 coats of Reactive Resins Armourguard. A flexible rubber in epoxy, tank coating , which is designed to exclude both moisture and air ( Oxygen) from the metal. It bonds well and copes with movement and temperature change. I the filled and faired the keel and applied a further coat of Armourguard. I also applied three coats of Reactive Resins TSF (totally solvent free) as part osmosis prevention on the hull. Then finally Coppercoat.

I am confident this will last more than the 7 years that it took for the previous treatment took to begin to have rust spots and more than the time it took for me to think I should address the rust. I am confident that It will outlast the copper coat and possibly outlast me. I will be able to confirm my optimism in another 5 years, I doubt that you can wait that long for conformation.

Unfortunately Reactive Resins went bust last year but as they say " other flexible tank coatings" are available.
Click to expand...

Can you epoxy over the PORS rust converter without any other preperation?

Is so, this looks like it might buy me a bit of time...

Rust convert as soon as the keels have been blasted, then epoxy later - before copper coating?
 
AMC supplied the correct primer to use on my keel prior to coppercoat. I applied it within 20 minutes of grit blasting. Unfortunately I erred & I did not apply enough coats (according to AMC) & i now have pitting after 5 years.
I imagine that if I had done it correctly it would have been OK so my fault.

However, rather than take various opinions I would suggest that you contact AMC & get the correct, compatible, primer.
 
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