# cast iron keel treatment



## kjones (Aug 4, 2011)

I have p26 who's cast iron keel was never properly treated. The marina quoted me near 1k to soda blast ad barrier coat the keel. I would try soda blasting it myself but the marina only allows its staff to do any soda blasting. The alternative would be for me to get out there with a grinder and do the thing by hand which I imagine could get old real fast. Questions are:
Is the marina price worth it?
Would hand grinding and barrier coating the keel myself be with the savings?
Or should I just leave the keel as is?


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## rugosa (Aug 30, 2011)

I've done this job too many times on customers boats (before soda we sand blasted with Black Beauty a slag bi-product), believe me, it's worth the 1k unless you are 20. Consider that they supply the space, labor, material, cleanup, warranty, disposal PLUS liability for contamination, complaining neighbors, EPA . . .


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## sailingfool (Apr 17, 2000)

I think the marina price is reasonable. While I would not take on stripping a bottom, I would do the keel myself and have done three or four in the past. Usually the stuff on a steel keel is not too well attached anyway, and I would think you could strip a 26 footers keel with a grinder in a few hours.

I would put five coats of West System epoxy over the clean metal, be sure to do the first coat as soon as you put the grinder down. There are several other threads about this prep.

Get it right once and you are not likely to need to do it again in the foreseeable future.


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## RobGallagher (Aug 22, 2001)

The marina price seems "reasonable", but we don't know about your financial situation or ability to do your own labor.

If it was me, I would do it myself. Materials will should run less than $400 and I would save or spend the other $600 on something else 

errr.... does that 1K include the haul out or is it already out? That could change my answer...


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## sawingknots (Feb 24, 2005)

the thing is about cast iron and rust is that the iron builds ir own protective barrier against futher oxidation [scales and rust] if you remove that barrier you only expose it to even more destruction,i doubt theres any sort of paint or other chemicals that will last long,i would just leave the existing rust/scale alone and only paint over it with antifoulent


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## kjones (Aug 4, 2011)

Are you saying that leaving the rust would not cause any long term harm or break down the keel? 

The boat is already out of the water. Itd be 500 or the soda blasting 150 for materials and 350 for labor. So in theory it'd only be costing me 800 since I'd have to buy materials also if I went at it myself. Thoughts? 
I'm leaning towards having the marina do it just to avoid messing it up my self and having it done right the first time.


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## RobGallagher (Aug 22, 2001)

kjones said:


> Are you saying that leaving the rust would not cause any long term harm or break down the keel?
> 
> The boat is already out of the water. Itd be 500 or the soda blasting 150 for materials and 350 for labor. So in theory it'd only be costing me 800 since I'd have to buy materials also if I went at it myself. Thoughts?
> I'm leaning towards having the marina do it just to avoid messing it up my self and having it done right the first time.


In that case I might pay the yard the $500 bucks to soda blast it. Then barrier/coat/ epoxy the thing myself. Applying the coats wont take long at all on a boat that size. You will probably spend more time mixing, waiting around for coats to dry and cleaning up. Not exactly back breaking labor


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## SloopJonB (Jun 6, 2011)

Pay for the blasting - you can't get the metal "white" enough with grinding and sanding. It also takes so long that the first parts have started to oxidize before you get the last parts finished.

There have been a number of posts about this process in the past. I'll dig up one of mine and re-post it - may give you some pointers.


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## SloopJonB (Jun 6, 2011)

*Iron Keel Prep.*

Here's some info on doing it properly for a long lasting, fair finish.



> From the research I've done it seems to me the best approach is to sandblast the keel white, then immediately apply a base layer of epoxy. Any recommendations as to what to use for the base layer? Is something like WEST systems alright, or is a zinc enriched epoxy necessary?


Sandblasting is correct - any grinding method will not clean ALL the pitted areas fully and future failures will start there. Just use regular epoxy resin as a seal coat - nothing fancy, just get it on right after blasting and a solvent wipe. You can't even leave this step overnight. West is only more expensive - 4 times as much as the industrial no-name resin I use. Stone fabricators - counter tops etc. use a lot of epoxy - check around and you'll save $hundreds.



> Moving on to a filler, again is WEST ok? and how many coats is recommended?


Again, West only costs more. Get a cement bag of industrial talc for about $20. It makes the most beautifully sanding filler you have ever experienced. Mix it to peanut butter consistency with epoxy and you probably won't even have any pinholes to fill after sanding.[/Quote]



> Many people claim to use a notched squeegee or trowel to apply the epoxy, and then fill in between the created lines? is this necessary?


This makes it MUCH easier to get an even coat. Unless you're an experienced plasterer, using a plain trowel will give you a very uneven thickness. You do NOT want to sand through to metal, ever, or you will have to start over there. You want a reasonably thick finished coat - 1/8" min. is my preference - in order to ensure the metal stays buried.

Get an autobody longboard sander - they look kind of like an old smoothing plane, about 18" long and take pre-cut strips of sandpaper. This will help you fair up your keel - mine ended up looking like it had been templated.

I finished mine off with 3 coats of epoxy resin and 3 coats of Interprotect (there was still discussion as to the best sealer at that time). Now I'd just use Interprotect for all coats.
__________________


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## SloopJonB (Jun 6, 2011)

sawingknots said:


> the thing is about cast iron and rust is that the iron builds ir own protective barrier against futher oxidation [scales and rust] if you remove that barrier you only expose it to even more destruction,i doubt theres any sort of paint or other chemicals that will last long,i would just leave the existing rust/scale alone and only paint over it with antifoulent


I think you are confusing iron with aluminium - iron will rust all the way through, given enough time. I had keel bolts that were corroded 1/2 way through and thin areas of my keel were completely perforated. Rust NEVER sleeps.


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## olson34 (Oct 13, 2000)

*Here's one method*

I used to know a yard owner that would routinely redo rusty iron keels. As others have noted, you Do need to get the corrosion off, and you Do need to protect themetalright away.

My friend used to tell me that the initial and invisible coating of oxide would start reforming within the hour, after the keel was cleaned "bright."

What he did was to immediatley (!) have epoxy at the ready and a low speed angle grinder with a disposable wire brush (or two) attached. He'd be out there in his tyvek suit and then put on the epoxy and Wire Brush it in, hard, into the iron surface.
The brushes would remove that new layer of corrosion and seal in the new epoxy layer in one step.
Once that was done and cured, would come the fairing and bottom painting.

Like sand blasting, grinding, or sanding, it's not any fun, but it Works.


LB


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## Rockter (Sep 11, 2006)

If it is cast iron, I would be inclined just to paint it.

Cast iron is remarkably stable against corrosion.

It corrodes very evenly, and very slowly indeed.


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## SloopJonB (Jun 6, 2011)

Rockter said:


> If it is cast iron, I would be inclined just to paint it.
> 
> Cast iron is remarkably stable against corrosion.
> 
> It corrodes very evenly, and very slowly indeed.


All due respect Rock - I have to question if you have ever SEEN an old iron keel that has not been cared for or protected.

Corrodes evenly and slowly? Maybe in a lab or in theory. In reality they corrode VERY unevenly, they get rough and downright lumpy. Slowly, maybe but only because of the large mass of iron.


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## sailingfool (Apr 17, 2000)

kjones said:


> .... and 350 for labor. ...
> I'm leaning towards having the marina do it just to avoid messing it up my self and having it done right the first time.


My concern is whether the yard will do the job so the result has a shot at being close to permanent. I would doubt that for $350 they will do five coats with fairing, and sanding of any highs as needed. I would do it myself because I am more confident that I would take the time to do the job thoroughly, which you may not get for $350...
Again this is a job that needs to be done correctly, or you'll face doing it again in two years.


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## sawingknots (Feb 24, 2005)

most boats that have iron keels are 25-30-years old and most are still fine if you disturb the natural barrier that has formed it will hasen the oxidation process


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## TQA (Apr 4, 2009)

If you get it blasted make sure it is done on a warm dry day and the epoxy goes on within 30 minutes.

I would use a zinc rich epoxy primer and for the first two coats and hi build after that. 

If you sand it make sure you wet sand /and / or wear a GOOD face mask. Epoxy dust can land you in hospital.


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## sailingfool (Apr 17, 2000)

sawingknots said:


> most boats that have iron keels are 25-30-years old and most are still fine if you disturb the natural barrier that has formed it will hasen the oxidation process


An untreated iron keel will be so rough it'll take a knot of speed off a sailboat. Combine it with a fixed blade prop and the boat will take on a pretty sluggish attitude. Most sailboats are slow enough when sailing optimally anyway, dragging the equivalent of an anchor behind you, would be well, a drag.


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## Faster (Sep 13, 2005)

sailingfool said:


> An untreated iron keel will be so rough it'll take a knot of speed off a sailboat. Combine it with a fixed blade prop and the boat will take on a pretty sluggish attitude. Most sailboats are slow enough when sailing optimally anyway, dragging the equivalent of an anchor behind you, would be well, a drag.


Further, the rust will not stabilize.. I had an iron keel that had been left untreated prior to purchase and I had an inch deep divot 6-8 inches across where rust had gotten a hold of things.

Besides that properly sealing an iron keel will prevent perennial rust stains, weeping and swelling that goes with rust formation. Subsequent haulouts will be much less labour intensive.


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## gbm4th (Jul 31, 2009)

I did it the hard way on my rusty iron keel with a grinder; very dirty job and it rusted up before I finished the other side of the keel. You will likely still have rust left over and lots of pitting.

I used Pettit Metal Primer with Activator to bond to the keel and leftover rust I could not remove. I than applied two coats of Interlux 2000 (read the directions carefully for timing with the metal primer) than applied fairing compound. After fairing the keel, another 4 coats of Interlux 2000 than bottom paint. Keel still looks good 2 years later.

Once you have done it, you never want to do it again. I would spend the $500 for the soda blasting and have them finish by noon so that I had time for one or two coats of paint that day.

Good luck,
george


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## fallard (Nov 30, 2009)

Haven't dealt with cast iron, but had a steel centerboard for 16 years. When I bought the boat the original owner had coated it with Rustoleum and--not knowing any better--I pt bottom paint on and launched it for the season. 

What a mess when I hauled for the winter! The Rustoleum failed, taking the bottom paint with it. The centerboard was exposed and further pitted all over.

The only thing that worked was having the board sandblasted and coating it immediately. The best treatment, when it became available, was Interlux 2000. I put it directly on the clean metal and built it up with several coats. It only failed where it got dinged when I had been "sailing by braille" in shallow water.

Subsequently, I have used a SS wire brush wheel on aluminum that was below the waterline. I just couldn't get to clean metal in the pits. I applied 2000 after using a zinc chromate primer and it held where there was no pitting.

The lesson learned: forget scraping and brushing. The only was to get to clean metal was sand blasting. I doubt soda blasting is aggressive enough to get all of the pits. Once you get to clean metal, IMMEDIATELY coat it. Zinc Chromate primer (thin coat) on aluminum, followed by 2000. Use 2000 directly on bare (shiny) iron or steel.


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## RXBOT (Sep 7, 2007)

Been there done it did it, spend the grand, let the yard do the whole job.By the time the job is over your enzyme levels will be going through the roof.Chemicals are nasty ,easier to let the yard take care of it all. And that seems reasonable price to me.


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## Lisle (Apr 21, 2010)

*Lisle*

I owned and ran a small boatyard for 10 years. The BEST treatment for almost any metal that is underwater is still Coal Tar Epoxy. 3 coats. No matter how the surface is prepared, sanded, blasted, wire-wheeled, etc.
While the third coat is "tacky", but NOT wet, put on the first coat of anti-foulant.
Best is blasting.
In any case, have fun.
Lisle


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