Cast Iron Keel Renovation - WS Epoxy vs. Barrier Coat first sealing layer - SailNet Community

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Old 12-12-2011
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Cast Iron Keel Renovation - WS Epoxy vs. Barrier Coat first sealing layer

Hello, This is my first posting to Sailnet, and actually to any forum such as this. I am a new sailboat owner, of a rhodes 19 Keel version sailboat. I am in the process of completely renovating it from hardware to the keel. I have ground down the keel to bare metal and am now debating what to do next. I have spoken to several other owners and received very good information that all is similar to what is typically posted on the internet. Primarily everyone says to use epoxy, then use epoxy with filler, sand, then bottom paint. One individual mentioned that if he were to do it all again he would use barrier coat instead of west systems epoxy as the first coat. What are peoples thoughts on this? As barrier coats have become much better over time, the barrier coats today are pretty much epoxy with water barrier ability and are rock hard. Could this be a better first sealing layer on the iron? I was also thinking of using OSPHO rust inhibitor to hopefully impede future rust development.

Any comments thoughts would be appreciated. Sorry for the length!
Ed
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Old 12-12-2011
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I did this early summer on my Catalina 22 swing keel (cast iron): Sandblasted to bare metal, 3 coats Interlux Interprotect 2000e, then bottom paint. Dove the boat after 6 months to clean and looks like it did when I finished. Time will tell. The Interlux was recommended by several local marine hardware places.

My understanding is rust begins immediately, so time is of the essence after sandblasting, as to not encapsulate the rust...
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Old 12-12-2011
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Thanks. I plan on regrinding/sanding before putting OSHPHO rust inhibitor on. After this drys and hardens. I will eventually resand again once more before then immediately sealing with epoxy or a barrier coat. I did not have the keel sandblasted so getting every bit f rust off is next to impossiible, hence my use of the OSPHO, which is supposed to chemically change any small remaining rust areas into a inert material that won't rust. I hope it works as marketed.
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Old 12-12-2011
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When I did the iron keel on my Columbia 43 I had it sandblasted and immediately coated with epoxy (not WEST - too expensive & no better than all the rest).

Because the iron was pitted, casting flaws exposed etc. I wanted to fair it up before putting a finish on it. I coated it with epoxy & talc, thickened to peanut butter consistency, using a 1/4" notched trowel. This left a surface 1/4" deep but full of grooves down to the keel surface. I then went over it again with a smooth trowel to fill in all the grooves. The result was a uniform 1/4" deep coat of filler. If you have the skill of a plasterer you can do this in one pass but I don't so this gave me a uniform depth.

I used talc as the filler on the recommendations of the yard owner - an old salt German who started life as a journeyman plasterer. It's dirt cheap - a cement bag of it was about $20. It also provides a beautiful surface for sanding - not too hard and leaves a very fine surface. I now use it exclusively for any filling that requires a "finished" surface.

Sanded everything with a 16" sanding board from an auto body supply shop - it uses pre-cut strips of 17 1/2" sandpaper. The board has a handle and knob like a hand wood plane and the strips of sandpaper clip on at each end.

Sand the filler diagonally, as you would any compound curved surface - car body, boat hull etc. Depending how corroded your keel is, you may have to do this process more than once. Be careful not to sand through to bare metal - if you do, IMMEDIATELY coat it with epoxy or filler to prevent oxidation from forming.

Once you are satisfied with the surface, wipe it down with solvent - acetone, MEK - whatever you prefer. Now you are ready for the final finish coats. I chose three coats of epoxy resin followed by two coats of InterProtect. This was mainly due to some rather widespread disagreement as to what was best at that time. I think now that I would use just Interprotect.

Now you're ready for bottom paint and if you were diligent during your filling and sanding, you should have the next best thing to a templated keel.

P.S. Grinding an iron keel isn't good enough - must sandblast. Every single iron keel I have seen hand prepped via grinding and wire brushing etc. has had a limited life before needing it again. Sandblasting means it will last WAY longer.
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Last edited by SloopJonB; 12-12-2011 at 08:34 PM.
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Old 12-12-2011
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Ed,
I used the OSPHO on my C22 keel after grinding it down to bare metal. Next, I used WS Epoxy. (BTW WS Epoxy IS barrier coat. It's one of several barrier coats out there). If you use West, just be sure to scrub it with soap and water and a scotch brite pad before you go to the next step.

For me, the next step was to build up a better foil shape of the keel using a fairing compound. After fairing the keel, I put on several more coats of epoxy barrier coat before painting with antifouling.

I did all that in 2007. Since then, the boat has been in a slip except for trailering to other sailing grounds, and hauling out for repainting the bottom. So far, no rust.
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Thanks Saildork! Do you mean to soap and water wash the OSPHO'd surface before applying the first epoxy coating? Let dry overnight or over several days, then light sand to prepare the surface for epoxy adhesion. I plan on using low density after the initial sealing layers of epoxy to fair the keel as well. I dont want to many layers because the boat will be raced and the keel needs to be as thin as possible.
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Old 12-13-2011
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I had good luck using Interprotect 2000 on the iron keel of my previous boat. Good adhesion and easy to apply.
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Old 12-13-2011
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Why not sand blast it? Rent a blaster? Is the boat/keel where you could do it?
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Old 12-13-2011
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The biggest issue with sandblasting is how good the air dryer is when the RH is 80 % and your shooting wet sand
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Old 12-13-2011
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While sandblasting is a nice way to go, it's not always practical or feasible. If you can't blast, do as you are doing, grind with a low grit (16 or less) angle grinder, then use a wire brush or drill mounted brush to clean out any existing depressions caused by rust.
Not familiar with the OSPHO stuff, but I used POR 15, probably similar. They are both nice in that they will react with any rust that does start to form, makes the timing much easier. Apply and sand. Repeat as necessary.
After that just smooth out with any epoxy/filler combo you like. Apply and sand, repeat, repeat, etc. Some fillers sand easier than others, choose wisely. It will take a few go-rounds to get it all looking good. After that apply a few coats of unfilled epoxy, hand sand between coats, then final sand up to 600 grit. Then paint with whatever you're using on the rest of the bottom.

It killed my knees crouching beneath the boat doing this. Wish I could have turned the boat upside down.
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