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jritchie 02-02-2001 06:22 AM

cast iron keel coating
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.

munchimike 02-02-2001 01:52 PM

cast iron keel coating
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.

jritchie 02-03-2001 11:01 AM

cast iron keel coating
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] ?

munchimike 02-03-2001 11:20 AM

cast iron keel coating
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.

jritchie 02-04-2001 08:07 AM

cast iron keel coating
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!!!!

munchimike 02-07-2001 12:21 AM

cast iron keel coating
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 visit my website.......maritimetradition, .Rev.

jritchie 02-07-2001 05:28 PM

cast iron keel coating
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!

Jeff_H 02-08-2001 02:32 AM

cast iron keel coating
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.

jritchie 02-08-2001 12:13 PM

cast iron keel coating
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?

Jeff_H 02-08-2001 03:19 PM

cast iron keel coating
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.

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:

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