# cast iron keel coating



## TSOJOURNER (Dec 16, 1999)

rust stains on the figerglass covering the cast iron keel led me to strip the fiberglass and start removing the rust . What is the best way to coat the keel and resheath: epoxy,fiberglas ,paint? This 38year old fiberglass sailboat is otherwise in great shape.


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## TSOJOURNER (Dec 16, 1999)

Sand as much of the metal to shiney as you can.Use a rust converter all over the exposed surface.Etch with a metal etch, or some converters double as etch. Penetrating epoxy, zinc-chromate, or other marine grade underwater primer for metal, Epoxy coating seem to last longer and hold better to metal. Double coat theareas under the foot.Shift your braces and try to move the keel pads back to access the areas that the boat is sitting on......Rev.


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## TSOJOURNER (Dec 16, 1999)

sounds good but why penetrating epoxy after metal etch? I''m thinking to minimize fiberglass work by mostly epoxy coating the keel then paint but would penetrating epoxy be better than regular epoxy[ like west systems] ?


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## TSOJOURNER (Dec 16, 1999)

Penetrating epoxy is one of those rare mystical products, sort of like the red lead of old; that has a fierce capability of bonding beyond. It''s service as liason between alien elements is invaluable.By all means use a fairing epoxy over it, and an epoxy paint.Your keel isn''t really the problem. The problem is guaranteeing that there is absolutely no rust and no moisture left within any region near this project!!!!---until you get a couple of coats of penetrating epoxy on it.There may be water involved in the rust converter process, and you must be certain that there is none left. I suggest a heat gun, or blowtorch or something.....don''t just leave it to Mother Nature .We are talking clinical D-R-Y-N-E-S-S-!-!-!Smith & Co. in Richmond Ca. are my preference over West, though they''re about the only mahogany micro-balloons I''ve found so far. Meanwhile layer a bit more strength onto the leading edge of the keel. Layer some glass cloth into that epoxy if you like, for that.......Rev.


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## TSOJOURNER (Dec 16, 1999)

Mike: i''ve heard of zinc chromate for steel--will that work for cast iron?
Does this sound like the process you recommend: clean until shiny,zinc chromate,dry!!!,penetrating epoxy twice,epoxy coat as required with glass cloth, coat with interprotect2000, anti-fouling paint.
thanks for the input!!!!


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## TSOJOURNER (Dec 16, 1999)

Well let''s hope that works. You could go to redlead if you were traditional, but it isn;t really too compatible with epoxy. The rust converter is the secret here. The trest is just to keep the water out!! Lotsaluck.Let me know next haulout how it [email protected] visit my website.......maritimetradition,homestead.com......Rev.


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## TSOJOURNER (Dec 16, 1999)

Mike: Any brand rust converter come to mind? The only thing I can find here in Ct is petit metal primer. There is West Marine,Boaters World, and Defender warehouse in my area so I can check them for specific brands. Thanks again for your help.I''ll check out your site tomorrow!


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## Jeff_H (Feb 26, 2000)

In terms of preparing the keel, I prefer to have the keel sand blasted white, and then immeadiately apply an epoxy coating. In industrial applications, ferrous metals are generally coated with zinc-rich epoxies.(epoxies with a high zinc content added.) These form a chemical as well as a physical bond and make a great primer. If you choose the right zinc-rich epoxy you should be able coat the primer epoxy coats with a conventional epoxy such as WEST System or MAS epoxy (I prefer MAS for a variety of reasons but WEST is a good product.) 

If you choose to skip the priming step then you can use a good quality epoxy such as WEST or MAS right on the iron. WEST actually has a good step by step decription of the process. I personnally like to use a layer of cloth any time that I do anything like this. I think that the resin had poor tensile characteristics and so is more likely to get small hairlines that let moisture in over time.

In terms of fairing the keel, by far the worst part of this whole business, I typically use a trowel that rectangular notches about an 1/8" deep and an 1/8" on center. I apply a first fairing coat of thickened epoxy with this trowel carefully getting reasonably vertical stripes. It is easier to work these down to fair first with a Red Devil body working plane and then with a long board. It is much easier to sand these ribs fair than a large flat surface. Once I gave these ribs close to fair,it is easy to fill in between the ribs with a tickened epoxy filler. I try to overfill the ribs and let it cure for a while after setting. I also dye the filler so that I can see when I have sanded down to the ribs. When all of that is done I then seal it all with a couple coats of epoxy as a barrier coat.

I check fairness with a batten and if I really care I make up a template by making a rough shape in plywood that I coat one edge with body putty. I tape saran wrap over the area that I want to match BEFORE I STRIP THE KEEL(I have on occation taken an impression on a sistership with permission) and press the body putty against the Saranwarp to get an impression that can serve as a template.

Done right this will our last any of us.
Good luck, I don''t envy you this project.
Jeff


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## TSOJOURNER (Dec 16, 1999)

Jeff: Where does West have their description of coating the iron keel? 
How do you deal with amine blush from the cured epoxy? Doesn''t that become difficult when you use a notched trowel?


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## Jeff_H (Feb 26, 2000)

That is what I like about MAS Epoxy, there is no amine blush. I have used comet and a toothbush in the past with WEST.
You can go to the WEST System web page.
http://www.westsystem.com/ 

They have a technical question link and they should be able to email the article on how to do the repair. 

You might also try the same question at MAS:
http://www.masepoxies.com/mas2.htm
Jeff


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## TSOJOURNER (Dec 16, 1999)

My thanks to all the input. I have started grinding on the keel and it''s obvious that there will be small minute areas where I can''t get all the rust out thus requiring the etching for treating.I''m going to be working in small batches until I can get a good coating over everything.
Has anyone used Petit metal primer or petit rustlock steel primer? 
I''m thinking that etching and then metal primer will allow me to get a coating on the new work as I progress and then epoxy over the primer on marm days.


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## TSOJOURNER (Dec 16, 1999)

cont: Using metal primer will allow me to grind, etch and prime one area. While the primer is drying[2hrs], I can move to another area and work.
I have reviewed the cold temp procedures from West Systems web site and it appears to be difficult to maintain proper epoxy working temperatures while working outside in the boatyard with limited facilities.


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## TSOJOURNER (Dec 16, 1999)

Don''t forget the rust converter...any hardware store will have it. About the temp.; I''ve seen people put up tents around their boats and bring in propane or kerosene heaters, and as you can guess-----it works!!!......Rev.


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## Jeff_H (Feb 26, 2000)

Reading you latest posts, I would suggest as a better alternative that once you gave gotten as much of the old filler off as you can, rent a sand blaster and blast the keel "white". I would at that point very quickly roll on a barrier coat. In my mind that would ideally be straight epoxy or an epoxy based primer. I would avoid any other primer except posibly a zinc rich epoxy or a coal tar epoxy if you intend to coat the keel with epoxy afterward. 

I would try to coat the keel in one session since the "laps" between cured and new epoxy are not as waterproof as a single continuous layer.

Jeff


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## TSOJOURNER (Dec 16, 1999)

Cost is the primary factor on this repair. i can grind and sand on the iron on my own but it is going to be small batch coatings until I get the whole keel coated.I checked on the different epoxy brands and it looks like there are compatibility issues.


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## TSOJOURNER (Dec 16, 1999)

Well maybe you should skip the epoxy. Do a rust conversion, that''ll take care of the sealing then just paint it with anti fouling. Next year you may need to do a touch up, but it''ll be done for now.


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## TSOJOURNER (Dec 16, 1999)

Mike--the problem is that the keel has to be faired into the fiberglass above the keel. It looks like the ''dutch'' cast iron was not perfect coming out of the mold. It has a deep gouge on one side about 2 inches below the keel/hull seam. This was faired with fiberglas when they built the boat and only showed when I stripped the failed covering.
The keel is very close to the hull sides until you get about 2ft away from the bow then it varies up to an inch or more.
I found out today that Mas epoxies can be used with rustlock metal prep so I''m coating the keel with the metal prep then sand, dry!!!! and then rub in a coat of epoxy to keep the moisture out.
I checked out the boatbuilding.com site and that''s a good source to know about!


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## TSOJOURNER (Dec 16, 1999)

I found that the metal prep would not last more than a day before the rust would start again so I''m coating the metal prep with pettit#6980 primer to stop the rust. This is just temporary until warm weather starts but it allows me to grind on the keel and have it sanded and primed .
Rust forms very quickly in one area of the keel because of porosity in the cast iron.I ground out a small area but found that the minute air holes went into the cast iron more than an 1/8 of an inch. Thankfully it seems contained in a one squre foot area.


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