Cast iron keel prep

[PabloPicasso]

Is it worth stripping a cast iron keel and epoxying it?

Seems like a lot of work, is it likely to be succesful in preventing rust in future? All I've done previously was to jetwash/Scrub, treat rust, prime, and antifoul.

 

[Concerto]

No, not worth epoxying a cast iron keel. Continue treating any areas of rust is the best policy.

When I purchased Concerto, the keel was in an OK condition. It was stripped back and treated twice with Fertan rust treatment followed by 5 coats of Primocon. When next lifted, there were areas where rust was active, so treated again. This has been repeated a number of times since. When lifted in August after 2 years afloat the amount of rust was almost negligable.





The lower part of the keel has been pushed through mud and shingle and broken through the paint layers, hence some rust there. Still nothing major considering it is impossible to seal under the keel.

 

[Tranona]

Yes, if you are prepared to have it blasted and coat it immediately as in the photos. Before and after. Coating is six coats of Hempadur and then Coppercoat. Blasting cost and Hempadur approx £450

Otherwise no. Local grinding, Primocon or similar and antifoul as per Concerto. Personally not convinced about the value of Fertan if you grind clean - it is a rust converter/stabiliser rather than a bare metal sealer.

 

[Travelling Westerly]

Tercco blasted entire keel, 2 coats of Fertan, 5 coats of Primocon and finally 2 coats of Tigre Extra. Felt pleased with it until I dived on it 2 months later. Let's just say I won't be bothering to do that amount of work again.!

 

[WoodyP]

Tercco blasted entire keel, 2 coats of Fertan, 5 coats of Primocon and finally 2 coats of Tigre Extra. Felt pleased with it until I dived on it 2 months later. Let's just say I won't be bothering to do that amount of work again.!

My view entirely. I am now down to spot treatment of the worst, Anti foul and back in. Nobody sees the work, and I am not that worried about a few scabby bits on my MAB.

 

[penfold]

Fertan on freshly blasted metal is a waste of money and may even have compromised the coatings laid on top.

 

[vyv_cox]

I have had my keel grit blasted twice, primed with epoxy (neither time in my presence) then Coppercoated by me. In both cases rust got underneath in 10 years, blowing the CC off.

 

[Tranona]

Tercco blasted entire keel, 2 coats of Fertan, 5 coats of Primocon and finally 2 coats of Tigre Extra. Felt pleased with it until I dived on it 2 months later. Let's just say I won't be bothering to do that amount of work again.!

Sorry, but the waste was in not coating properly with epoxy if it had been blasted to the right finish. The Hempadur to do my keel above cost less than £100. Bit tedious to apply the necessary coats - took me 3 days. another £200 or so would have got you Coppercoat as well.

 

[dankilb]

Fertan on freshly blasted metal is a waste of money and may even have compromised the coatings laid on top.

Omg I can’t think of anything worse to apply before a coating.

Epoxy primers will adhere (and may replicate if not exceed the protection offered on original castings - i.e. 15-20 years) if applied after proper blasting.

Leave rust converters way out of the equation (unless you only want a couple of years’ protection with vinyl primer and AF).

 

[Spirit (of Glenans)]

Yes, if you are prepared to have it blasted and coat it immediately as in the photos. Before and after. Coating is six coats of Hempadur and then Coppercoat. Blasting cost and Hempadur approx £450

Otherwise no. Local grinding, Primocon or similar and antifoul as per Concerto. Personally not convinced about the value of Fertan if you grind clean - it is a rust converter/stabiliser rather than a bare metal sealer.

When buying my previous boat, the seller advised me to grind clean, leave overnight, then apply rust converter.

 

[Tranona]

When buying my previous boat, the seller advised me to grind clean, leave overnight, then apply rust converter.

I do hope you did not follow his advice.

 

[Kelpie]

I asked a similar question a few days ago. I'm still a bit confused about the options for primers.
Looking at SVB24 (boat is in Spain) I can choose:
- Epotec Epoxy primer
- various one-part primers
- VC Tar
- Interprotect

The epoxy one is only EUR17 a tin, the same price as e.g. Primocon. Surely it's a no brainer to go for it, or is there some downside?

 

[ghostlymoron]

I came to the conclusion years ago that the only way to keep the keel rust free is to grit blast to Swedish standard 2.5, epoxy prime, top coat and store under cover from then on.
Realistically, blast clean, epoxy prime immediately, apply top coat and anti foul. Carry out spot treatment in subsequent years including blast treatment. Basically the same system as used on oil rigs.

 

[Kelpie]

So should I be epoxying and then applying a second conventional primer on top of that, before AF?

I don't really want/expect to have the boat out of the water very often (we are living aboard and are on a fairly small budget). We're only lifted just now because of an emergency trip home, and we will only have a couple of days to prep the keel before we launch.

 

[dankilb]

So should I be epoxying and then applying a second conventional primer on top of that, before AF?

Yes! In theory (i.e. TDSs!) a tie coat of underwater primer is recommended between epoxy and AF.

I say ‘in theory’ because I personally couldn’t say why! Sure someone will know…

 

[Spirit (of Glenans)]

I do hope you did not follow his advice.

I did, every year

 

[dankilb]

I did, every year

There may be some vague logic to that - namely, leaving overnight allows flash rusting to occur and gives the ‘converter’ something to convert.

As others have said, best get to clean metal (blasting ideally) and immediately coat (not with rust converters which - despite what they claim - are not primers). Priming after blasting gives maximum adhesion, immediate protection, and minimum (flash) rusting and contamination - in theory.

 

[Tranona]

I did, every year

Why would you want to do that every year? If you are looking just at patching every year then just Primocon after grinding is the way to go. If a longer solution is sought then blast/epoxy is worth considering. Just can't see any benefit in letting a clean bright metal go rusty so a rust converter can be used.

 

[Kelpie]

Given that I only have a couple of days to do this job, maybe epoxy/primocon/AF is a bit overkill? Just grind back and prime?
OTOH I don't know when we will next lift out.

 

[Tranona]

Forget epoxy. Primocon is easy stuff - as many coats as you can get on in the time you are out of the water. Jotun Vinyguard is a good alternative to Primocon if you can get it, much cheaper and just as effective, but only available in 5L cans - around £30 in UK.