Treating and protecting rusty keels

[AntarcticPilot]

When I Coppercoated Capricious, AMC recommended the use of an epoxy zinc-rich primer on the keel. No idea how well it will last - it only went on last year, and with one thing and another, she's only been in the water 9 months since then.

 

[rudolph_hart]

I did the iron wing keel on my Dehler 35 myself in 2009, as follows:

1. Use a 'nail gun' to remove all the coatings
2. Use an angle grinder, first with a metal sanding disk, then a wire brush
3. Brush off then treat with rust converter.
4. Fill/fair any holes with SP Epoxy resin mixed with micro-balloons
5.Apply two thick coats of Jotamastic aluminium primer (buy from Shepherd Marine in Clapham, London), sanding between coats
6. Apply one coat of Antifoul Primer.
7. Apply Antifoul

Allowing for overnight curing etc, the whole thing was done in 3 days & the keel is still as good as new.

 

[Fimacca]

I have tried various options such as mentioned before after a good old grinding down. (not epoxy) every year rust spots show through. cosmetic - just make it part of the annual pre launch work to treat it...............and forget !

or get lead keels if you are that way inclined !

 

[Seajet]

On a boat with mild steel keel plates I steadily improved them by grinding back the suspect bits to bare metal then quickly using Hammerite primer before two coats of smooth Hammerite. Antifoul on top.



The protected area gradually grew in size over a few years. The primer seemed to be the key to the success of the process.

I believe Hammerite are now owned by Dulux so the two products may be the same thing but badge engineered.

I don't think so if you're referring to Dulux Metalshield; don't be misled by the ' Dulux ' name, that stuff is dynamite, I have had steel keels for 37 years and replaced one keel after trying every steel treatment going - I used to work in a chandlery so had discounted access to all the steel treatments like Primocon, Galvafroid, Fertran, Blakes, etc etc.

I wouldn't trust Hammerite to paint a steel ( or alloy ) garden ornament, but the Metalshield is quite remarkably good on keels; my father is like me an engineer but a lot moreso, when he saw the results with Metalshield after all these years of trying stuff, like me he was pleasantly amazed.

I would add that I have always believed in very thorough preparation before any treatment, and I am not on a commission from Dulux !

 

[ghostlymoron]

I can't see how any pre treatment except blasting to SA 2 1/2 can work due to the imperfections in cast iron. If any dross is still present, corrosion will occur. The most likely place for rust to re occur is at the joint with the hull unless the keel is removed and the top surface treated. This is a bit OTT in my opinion to treat what is only a cosmetic problem. Probably a realistic approach is to grit blast with the keels attached, several coats of zinc rich primer followed by your choice of AF.

 

[Gwylan]

Last year I aquired a nice little bilge keeler that had not had any attention for some years. It was hauled out and, amongst other jobs, the keels where cleaned back to bare metal, treated with Kurust and a few coats of hammerite before anti foul. The boat is now back in the yard and rather frustratingly the keels haven't fared well. Can anyone suggest a more durable treatment, which undoubtedly will be starting from bare metal again?

Has a familiar ring.

We combined it with a soda blast of the rest of the hull before doing the CopperCoat.

After a couple of seasons we found that the foot of each keel was being rubbed every time we dried out and rust was appearing.
So on one lift in the Netherlands we slapped a couple of coats of cheap anti rust paint on the bottom 6 inches of the keels and the underneath. Then on top of the paint we put strips of fibreglass bandage and slapped resin over the lot.
Required a modest bribe to the crane driver to lift the boat a few centimtres off the the ground and stand her on timber blocks and go away.

That was 2008. The anti rust paint, whatever it was has been amazingly good. Cannot find it again of course.
The bad news in all of this was that the paint was a violent yellow but it still works as an excellent indicator when the resin coat is being worn away and ready for a top up.

 

[rgarside]

I have a Parker 275, I have used the KBS preparation and paint system on the cast iron keel and it stands up well. After I bought the boat I lifted the keel out and had it grit blasted, then used the KBS system. Subsequently touching up any local grounding damage has presented no problems.

KBS is more commonly used on car chassis, but the recommendation for marine use is to give it an additional coat - it seems to work well.

The system has a de-greaser, a phosphate etch, and a 1-pack paint.

 

[KellysEye]

Having owned a steel boat I can assure everybody that rust treatments don't work, as the OP proved. Grind back to bare steel when the humidity is low or you risk flash rusting then apply two coats of Zinc rich epoxy primer, then anti fouling.

 

[richardsn9]

I can recommend Jenoseel anti-rust paint, I found it better than Hammerite on my Centaur keels. It lasted much longer but, as many have said, it is only a matter of time before the rust returns......

 

[Sailingsaves]

As a first, cheap attempt, how about angle grinding with a wire brush attachment.

Treat with phosphoric acid - paintbrush job.

Prime and paint.

Phosphoric acid on ebay, get about 75%

Tannic acid mixed with an adhesive primer also works well - better than Jenolite (MOD use it) and all the other branded rust 'cure' names.

 

[VicS]

As a first, cheap attempt, how about ..........................................................................
.................

I think that's the sort of approach the OP has already taken with disappointing results and why he is now asking for a "more durable" treatment.

 

[Sailingsaves]

I think that's the sort of approach the OP has already taken with disappointing results and why he is now asking for a "more durable" treatment.

But don't you think phosphoric acid will be an awful lot better than "Kurust" or whatever they call it?

It will remove all iron oxide (even without wire brushing actually) and leave a protective oxide coating ready for decent paint?

In fact, it may prove a long lasting treatment may it not?

That spanner I showed you guys ages ago has not rusted again and all I did was dip it in phosphoric acid. The oxide has prevented further rust without paint.

But you're the chemist, not me. What do you reckon?

 

[KellysEye]

>As a first, cheap attempt, how about angle grinding with a wire brush attachment. Treat with phosphoric acid - paintbrush job. Prime and paint. Phosphoric acid on ebay, get about 75%.Tannic acid mixed with an adhesive primer also works well - better than Jenolite (MOD use it) and all the other branded rust 'cure' names.

It won't work and will be compounded by small bits of wire on the steel from the wire brush . I aso said no rust converter works as everyone on here who has used has said. As I said the only way to stop rust returning is grind back to bare metal when the humidity is low otherwise you risk flash rusting. Then apply two coats of Zinc rich epoxy primer, the rust will not return.

 

[Pauly]

Right-ho you lot, thanks to all the input I think I have come up with a plan. The keels will get spot treated for now with wire brush and sander, followed by hefty application of whatever jollop I have to hand and a/f to finish Then in the summer when it's warmer and dryer I'll get the boat back in the yard and go the grit blast route. I think a large contributing factor in the failure of last years efforts was the inclement weather when I was working on the boat. I obviously tried to mitigate the dampness as best I could, but clearly I was pissing into wind. (Not literally of course ).

 

[Sailingsaves]

>As a first, cheap attempt, how about angle grinding with a wire brush attachment. Treat with phosphoric acid - paintbrush job. Prime and paint. Phosphoric acid on ebay, get about 75%.Tannic acid mixed with an adhesive primer also works well - better than Jenolite (MOD use it) and all the other branded rust 'cure' names.

It won't work and will be compounded by small bits of wire on the steel from the wire brush . I aso said no rust converter works as everyone on here who has used has said. As I said the only way to stop rust returning is grind back to bare metal when the humidity is low otherwise you risk flash rusting. Then apply two coats of Zinc rich epoxy primer, the rust will not return.

Did you mean your post to come over as adamant as that? I do notice that you post predominately in the Lounge.

My eyes must be deceiving me in this video I made of phosphoric acid removing ALL iron oxide and the spanner is to this day protected by the phosphate coating. That was on a scrap spanner and no wire brushing. I did not have to remove it to bare metal as you can see.

https://www.youtube.com/watch?v=A1pDvt5CZqQ

But your post seems to imply you are the expert, so to the OP, if you don't wish to try 75% phosphoric acid, for a few quid and a few miutes of paintbrushing that is up to you of course.

Could you explain what I have done in my video if it has not removed all the rust "as everyone on here who has used has said..." it cannot possibly have done.

 

[Sailingsaves]

Right-ho you lot, thanks to all the input I think I have come up with a plan. The keels will get spot treated for now with wire brush and sander, followed by hefty application of whatever jollop I have to hand and a/f to finish Then in the summer when it's warmer and dryer I'll get the boat back in the yard and go the grit blast route. I think a large contributing factor in the failure of last years efforts was the inclement weather when I was working on the boat. I obviously tried to mitigate the dampness as best I could, but clearly I was pissing into wind. (Not literally of course ).

I would recommend (despite Kellyseye stating it does not work) trying this:

http://www.ebay.co.uk/itm/Phosphori...797309?hash=item1ea287563d:g:dBUAAOSw9N1VyRgE

or from any other seller (smaller quantities available)

with a paint brush.

Don't even wire brush.

Let us know if I am as wrong as Kellyseye states. Try not even painting an inch that is treated and see if it remains grey and protected without paint.

 

[KellysEye]

>Did you mean your post to come over as adamant as that? I

The reason I was adamant is I owned a steel boat, I tried a number of rust converters and none worked, as everyone who has used a converter here has said, the rust always comes back. Then I read about Zinc rich epoxy and never had a rust problem again. But as I've said wait for low humidity tt avoid flash rusting.

In your video the steel is pitted a grinder removes that and the last thing you want to do is wash bare steel it would much worse than flash rusting.

 

[vyv_cox]

Right-ho you lot, thanks to all the input I think I have come up with a plan. The keels will get spot treated for now with wire brush and sander, followed by hefty application of whatever jollop I have to hand and a/f to finish Then in the summer when it's warmer and dryer I'll get the boat back in the yard and go the grit blast route. I think a large contributing factor in the failure of last years efforts was the inclement weather when I was working on the boat. I obviously tried to mitigate the dampness as best I could, but clearly I was pissing into wind. (Not literally of course ).

Don't use a wire brush. Cast iron is partly porous and contains relatively large amounts of graphite in rosette form. Wire brushing drives the rust into these areas, where they will rust again in a very short time. Use an angle grinder, which does not have the same effect. It is perfectly possible to touch up small areas with one.

 

[Sailingsaves]

>Did you mean your post to come over as adamant as that? I

The reason I was adamant is I owned a steel boat, I tried a number of rust converters ...

Didn't try them all though, so no reason to be adamant.

In your video the steel is pitted a grinder removes that and the last thing you want to do is wash bare steel it would much worse than flash rusting.

As I said and as the video shows, all rust has gone and NO steel is left showing; it is all covered in protective phosphate, so it can be wet as one likes. The spanner lays on a brick wall in the garden and has not rusted.

So added benefit is no waiting for a low humidity day - good luck with that one.

I think it could solve the OP's problem easily. The epoxy you mention would be great to fill in the pitting.

Grinding would remove good steel as well as the rust but would result in a smooth (and thinner) keel.

Overall I think the phosphate treatment requires the least amount of work and money and there is even a video to show it works as opposed to a bunch of sailors stating what does, might or has worked.

But it is up to the OP.

I won't tell him or anyone else what is correct, but if you wish to tell me I am wrong again, water duck's back now.

 

[VicS]

As I said and as the video shows, all rust has gone and NO steel is left showing; it is all covered in protective phosphate, so it can be wet as one likes. The spanner lays on a brick wall in the garden and has not rusted.

I think it could solve the OP's problem easily.

Very probably if the OP could immerse his keels in phosphoric acid until all rust etc was removed and then just leave on the garden wall they would remain rust free , just like your spanner.

Unfortunately immersing the keels in phosphoric acid may be more difficult than immersing a spanner, and he will then be wanting to withstand immersion in seawater 24/7 rather than adorning the garden wall.

It really is not a valid comparison.