Keel rust treatment, then antifoul.

[PeteCooper]

... as it was recommended to me by an independent paint expert, an ex lecturer on the subject; sadly I can't ask him further as he is no longer with us.

With all due respect to your late friend I suspect that Dulux have access to more data re their products than he did - and probably more extensive test facilities.

As I said initially I should have asked Dulux for the reason when they replied to my e-mail - but I didn't.

... ground it clean with angle grinder and flap discs, applied five coats of Primocon and the rust was showing through before the boat was launched. The paint is very viscous and does not flow well ...

That is what I had found in previous years ... but in my year of Primocon success I found some instructions that said to thin the first coat ... I can't remember the amount of thinners, but something like 20% rings a vague bell and no rust is showing.

 

[Seajet]

' You can lead a horse to water '...

You've heard from a well respected engineer - and boat owner - of these forums,

and direct personal experience from a trained engineer and boat owner who's tried every treatment on the same keels for 40 years ( and a few more years on other keels ).

Coat your keel/s in milk chocolate if you like, I'll be using Metalshield.

 

[PeteCooper]

' You can lead a horse to water '...
You've heard from a well respected engineer - and boat owner - of these forums,
and direct personal experience from a trained engineer and boat owner who's tried every treatment on the same keels for 40 years ( and a few more years on other keels ).
Coat your keel/s in milk chocolate if you like, I'll be using Metalshield.

What a strange response ... I haven't even disagreed with you ... except to say that my experience with Primocon has been very positive. I also gave you a direct quote which I copied and pasted from somebody at Dulux.
I am also a trained engineer and worked as a design engineer for many years, although I don't see the relevance in this case as I only worked with a few different coatings, and have been trying different potions on keels for a lot longer than 40 years.
I don't care what you coat your keel in, and I don't expect anybody to care what I use, all I have done is provide a fact from a manufacturer and some personal experience - which is as valid as yours.

 

[Seajet]

My response isn't strange at all...

You didn't provide any backup gen' except some Dulux bloke who might well deal with greensheds or something; the chap recommending ' Metalshield ' to me was a lecturer / professor on paint polymers, also a lifelong boat owner.

However as I said if you disregard people with direct knowledge & experience trying to help, suit yourself.

 

[Jaguar 25]

I have tried every paint and steel treatment on my 3/4" galvanised steel lift keel over the last 39 years.

THE one treatment which stands out head and shoulders above the rest is

Dulux Metalshield, it's brilliant stuff.

One part, but requires the one part Metalshield undercoat.

Available from Brewers, £ 29.00 for each 750 ml tin, but worth it - on a well prepared steel, iron or alloy surface - in /or v close to Langstone Harbour.

As for antifoul, last season my usual Cruiser Uno was useless, so I and most people I know are switching to Seajet a/f.

Since you are in the same area as our boat I think I will take your advice.

Simple question first; presumably I just coat (primer then topcoat) the area where the rust has been ground back on the keel and do not overpaint the other non-rusting areas?

Finally, thank-you for all the other suggestions.

 

[Marakei]

I used Primocon last autumn on the rusty and pitted cast iron keels of my 51 year old Westerly 22.

Just to endorse the idea of using thinner.

I couldn't get Primocon into the pits in the metal at all before using this, but when thinned according to the instructions on the tin, it became quite nice to work with.

There are a few rust spots on the keels now, but as they were very rusty before I started working on them, I feel the results have been as good as expected.

 

[Seajet]

Since you are in the same area as our boat I think I will take your advice.

Simple question first; presumably I just coat (primer then topcoat) the area where the rust has been ground back on the keel and do not overpaint the other non-rusting areas?

Finally, thank-you for all the other suggestions.

Grind / wire brush everything off the keel surfaces as much as you possibly can.

Brush on Dulux Metalshield ( as I say, Brewers sell it, don't even look for it in Homebase etc ) Undercoat.

Next day, brush on Metalshield topcoat - I think it comes in white or black, I use white.

Hope to meet you out there, though I'm on the other side of the bridge - sail no. 119.

Andy

 

[Seanick]

As a boatbuilder, the only treatment I undertake to keels that I have found economic in the long term is..

Shotblast on a dry day.

No Fertan or Vactan.

Epoxy coat within 15 minutes (We use Bradite EU 96), then epoxy fill between each further coat of epoxy.
Apply at least six coats with a 4" fluffy roller, not a foam roller.
Apply one or two coats per day.

On the last coat, when tacky, apply either one Primocon, or antifouling primer. When that is tacky, apply the first coat of antifouling.

We have found this gives, within reason, at least ten years rust free .

If we are applying copper (Reactive Resins 'Synergy') we stiil give any keels the above epoxy treatment, so save the keels becoming the anode as the copper becomes a major cathode!

Any other approach seems to last only a season.

 

[Seajet]

I'm afraid ' Synergy ' sounds like an inappropriate marketing bullshit buzzword used out of context - do they even know what it means ?!

As I mentioned quite a few posts ago I think epoxy on keels is a bad idea, as any chip will mean salt water trapped alonggside the metal; this might seem an obvious byproduct of a boat afloat, but seems to matter with boats on half tide moorings - it certainly seemed significant with my first galvanised mild steel keel.

I fit a normal sacrificial anode, in the case of the Anderson 22 the usual answer is a ' flying saucer ' disc anode cut in half ( so it does 2 seasons ) bolted to the forward bit of the lift keel so it doesn't interfere with the thing going up & down; I fair it in with plastic padding as otherwise the turbulence from the supersonic wake would set off submarine SOSUS listening systems from here to Mars.

 

[Seanick]

Hi Seajet,

The Synergy works well, better than Coppercoat.

My own boat is on a shallow mooring, and sticks a foot or two in the mud at LWS. Therefore it's a coat of Primocon and lots of anodes to preserve the shoe.

The epoxy on the keels, correctly applied, onto bright freshly blasted steel or iron, is pretty much an industry standard. It's a proper chemical bond to the substrate, and cannot be compared to any other method. It's worked well for my customers over the last 29 years in the trade.
Rgds
Nick.

 

[Seajet]

Hi Nick,

with all due regard - and I actually mean that ! - I can't help thinking that's ' an industry standard most economocal we can get away with ' - please don't be insulted, British Aerospace did this all the time, though as we tried to warn them they came unstuck trying it on the Indian Navy...

If you haven't tried Metalshield give it a go, you'll be amazed.

Andy

 

[sailorbaz]

Hi Jaguar,
I guess you know your boat is a UK built Catalina 25. I have the same boat built in Australia as a Boomaroo25 but mine has a cast iron swing keel - not sure if any of the UK ones had the swing keel. Anyway I was told that all the keels for US and Aussie boats were cast in a back yard type foundry in Mexico. I don't know if the UK ones were too. Mine has lots of pits and blow holes and could not be described as smooth! Mine is in the yard at the moment after two years in the water and the keel only had a few spots of rust mainly in the pitted areas. I have treated it the same as last time - wire brushed the rust, put rust converter on the rust only. Antifoul undercoat on these areas, then two coats of antifoul with a third coat down the leading edge.
Sailorbaz

 

[rogerthebodger]

As a boatbuilder, the only treatment I undertake to keels that I have found economic in the long term is..

Shotblast on a dry day.

No Fertan or Vactan.

Epoxy coat within 15 minutes (We use Bradite EU 96), then epoxy fill between each further coat of epoxy.
Apply at least six coats with a 4" fluffy roller, not a foam roller.
Apply one or two coats per day.

On the last coat, when tacky, apply either one Primocon, or antifouling primer. When that is tacky, apply the first coat of antifouling.

We have found this gives, within reason, at least ten years rust free .

If we are applying copper (Reactive Resins 'Synergy') we stiil give any keels the above epoxy treatment, so save the keels becoming the anode as the copper becomes a major cathode!

Any other approach seems to last only a season.

This is exactly how I did my steel boat.

The Epoxy I used was 6 coats of Epoxy tar. This is less hygroscopic than other types of epoxy and is also more flexible and less likely to chip.

My boat has been afloat for almost 10 years and inspected and anti-fouled every 2 years with no sign of rust. My anodes that are bolted to welded on studs also show very little erosion just enough to show they are working without over erosion.

 

[GHA]

Please let me know where shotblasting & epoxy is the most economical, I'll set off this afternoon

 

[rogerthebodger]

Please let me know where shotblasting & epoxy is the most economical, I'll set off this afternoon

This is when and where I did mine.

Just let me know your ETA.

 

[GHA]

Just let me know your ETA.

Load of work, innit. Nice looking boat.


Possibly seajets wire brush and a tin of dulux might come in a bit cheaper.....

Ameron is my favourite paint at the moment, especially the sealer when shot blasting isn't an option.

 

[rogerthebodger]

Load of work, innit. Nice looking boat.


Possibly seajets wire brush and a tin of dulux might come in a bit cheaper.....

Ameron is my favourite paint at the moment, especially the sealer when shot blasting isn't an option.

BTW dont ask for shot blast, specify grit blast, it gives a much better/rougher surface for the paint to adhere to.