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Thread: How to protect a cast iron keel?

  1. #1
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    Default How to protect a cast iron keel?

    What are the options for protecting a cast iron keel from rusting and fairing its rough exterior? Having taken it down to clean bare metal it is rough and lower than adjoining surface. What next? The previous owner had applied epoxy from the looks of things. It didn't protect the metal i.e. keep it from rusting. the outside looked nice until a closer inspection showed some blisters. Popping reveiled big flakes of rusted metal. I don't want to repeat that experience.
    thanks

  2. #2
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    I just finished working on a Garden double-ender that had an iron keel. The owner had epoxied over it 15+ years ago. Sounds similiar to yours - bubbling up, heavy rust underneath, and heavy pitting.
    This is how I did it:
    First I peeled /scraped off the worst of it. I took a 7" sander to the whole thing (wear your respiratory mask and goggles and what-not - it's a horrible job - iron,epoxy,and bottom paint dust). Then I cleaned it with solvents and started my epoxy work the same day to avoid any oxidation of the iron. Then I filled the pitted areas with thickened epoxy. Sanded that back and followed with a second thinner coat with a squeege. Faired that, filled again, then faired again. Resulted in a very smooth fair surface that looked like new. Maybe it will last another 10-15 years?


    Last edited by Stephen; 08-06-2006 at 12:32 PM.

  3. #3
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    This is an iron keel on a 1962 Rhodes 18 (current photos).


    I believe it came poly-fiberglassed from the manufaturer - including the top. I think at the time of purchase the manufacturer gave the option of glassed or not. NOTE: I think it is important that the "glassing" of the keel included the actual use of fabric - not just poly or epoxy coating.

    Prior to my purchase it lived in salt water.

    I purchased the boat 11 years ago and repaired some spots on the keel with epoxy/glass - including a substantial breach on the forward edge/lower corner where it apparenly interacted with a rock. I used glass fabric and epoxy for the repairs. I coated the entire keel with 2 or 3 coats of epoxy. It was then primed with two coats of Awlgrip 545 Epoxy Primer (2 part) and top coated with Detco Sterling 2 part Lpu. I have not touched it in 11 years.

    It currently lives on a trailer and spends most of its sailing time in fresh water. But, it has also been in moored in salt water for up to two weeks at a time - on an yearly basis.

    I'm not actually answering your question, but showing you what has been done and is working in my situation.

  4. #4
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    For a lifetime keel job.

    1) Blast to white metal, Make SURE you get all the rust out of the pits.
    2) Phosphoric amine wash
    3) Wash with ethanol, not methanol or denatured
    4) 3 thin layers of coal tar epoxy, NOT normal glueing epoxy
    5) Abrade, but don't pierce the surface
    6) Apply fairing compound and fair, again don't pierce the coal tar surface.
    7) 2 thined layers of MI Formula 150 undercoat
    8) 2 thined layers of MI Formula 152 build coats
    9) Finish with MI Formula 153 anti-fouling or the anti-fouling of your choice.

    Works every time.
    Last edited by John E Hardiman; 08-06-2006 at 12:00 PM.

  5. #5
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    Thanks gents.

  6. #6
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    There is a little known industrial primer for steel and cast iron on the market known by the trade name "Dev-Con Z" This is literaly the closest thing to hot dip galvanizing that can be applied by brush or spray. It should be applied directly to a raw sand blasted surface. After the product has dried it can then be coated with red lead, followed by bottom paint. This is more effective than applying an epoxy coating as it insures a moleculor level of zinc bonding to the ferris surface which is further enhanced by the addition of red lead as a primer.
    JG

  7. #7
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    John, You know the Forum won't know that MI stands for "Mare Island Naval Shipyard". You also know folks on the forum will have a hard time obtaining paint invented by a closed Shipyard. And you know there are competing products that will yield the same results.

    I know that the paints you recommended are good ones and you remember them off the top of your head (as do I). I think you need to simply refer to commercial marine paints designed for steel vessels for equivalent performance. Paint manufacturers have great products these days. You could also refer the specification for these paints such as MIL-DTL-24441. It includes substitutes that give equivalent performance.

  8. #8
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    Bainbridgeisland.....just Google it!, you'll get 10 hits all from paint producers!

  9. #9
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    According to the industrial painters in a company I used to work for, coal tar epoxy is the ONLY coating that is absolutely impervious to water.

  10. #10
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    The results from any good coating system are often proportional to the surface preparation, and adherence to the manufacturers' related instructions.

    Sand/grit blasting is often the preferred professional initial step. When washing casually [not in accordance with manufacturers' prescription] a metallic surface that has NOT been grit blasted (and HAS endured brine immersion) , there is some value in washing with detergent, then rinsing in fresh water, and finally rinsing with distilled water {i use a chip brush to apply the rinses to areas with inconvenient access}. The water is a good solvent for salts , which are corrosive and hydroscopic . Alcohol may also be , but i dunno that.

  11. #11
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    Quote Originally Posted by TMny
    The water is a good solvent for salts , which are corrosive and hydroscopic . Alcohol may also be , but i dunno that.
    The phosphoric amine wash takes care of the salt and surface rust (which in a marine environment, i.e. shipyard, occurs as soon as you stop working the bare metal surface), the alcohol is to asure adhesion of the coal tar (gets rid of oil, fingerprints, sweat drops, etc).
    Last edited by John E Hardiman; 08-08-2006 at 10:17 AM.

  12. #12
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    Chralotte, VT
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    Interlux 2000E epoxy barrier coat. 8 coats by roller or 10 mill spray. But proper prep is important blast/acid wash/solvent wipe/paint immedatly.

  13. #13
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    After several acid washes, coating and fairing, I don't put the topcoats on keels for at least four weeks or longer if possible. After four weeks I'll fair again and then probably again and then again. Then I paint the top coats. Fairing, I use epoxy and high strength fillers (compression strength fillers) or epoxy and glass bubbles, or a polyurethane filler then epoxy over the top of the polyurethane.

    I think working on metal keels from being rusty, is about the most fun you can have working on boats. A metal keel no matter how bad they are initially, will reward good sustained work ... unlike wood.

    I agree with tar coats being fine and doing a job well. I don't do tar coats or the thicker rubberized tar coats (from blasted bare metal that is) I like high tech epoxy metal primers. The old tar coats that I've worked generally tend to belie their age, by many years. They certainly describe how well they work. I use epoxy because the tar coats sweat out making painting more difficult.

    I'm working on a metal keel now (Catalina 22, this week) that I started 12 weeks ago, and put away for 11 weeks for the epoxy to cure. The shrink rate has been excellently bad and very enjoyable. The owner now sees the reason why waiting before painting was wise.

    I called this keel on a Flying Fifteen (below) the makeover from hell ... but hell was the whole boat.





    Attempting to put hell's fires out (below). The power wash took the seafood and old paint off ... but that was all it got off. Drastic action was needed ... sparks. I notice with the keels, when they are cast, they are not finely shaped and finished, creating sparks helps. The keel was also sandblasted and then sealed with the epoxy metal primer within minutes of finishing the sandblasting.





    This photo below was supplied by the Catalina's owner. All other images on this post are mine.





    After blasting and several acid baths the epoxy went on well.





    Getting into a bit of sculpture, the start of reshaping of the Catalina's foil.





    The shape of the foil after the fillers. This foil lost this shape (below) thanks to the epoxy shrinking, so I've faired it again. When people say she doesn't need the work just put her on the water, she will do, their boats get to go nowhere fast.





    This was a classic fix of a greasy tar coat. The light brown colour through the white epoxy paint is the tar oil that had sweated out. We faired this Sonata 6.7 keel with a grinder and repainted it all in under two hours. Epoxy primer (grey) builder's bog (pink) and then slapped on a couple of coats of 2 pack water based polyurethane and instantly dried and hardened the paint with a heat gun ... the boat won two hours later. We did the job in the morning before the race. This was a quick and dirty and I did enjoy the speed of this job ... but never again.





    The keel did end up looking good ... but I've been too scared to ask her owner how is the keel now, a month later . If it has held up at all and retained it's shape it is probably a miracle. The blue tape below indicated where we still needed to fair, a perfect job for minimalists boat boys. It was that the tar coat had held it's age well, that allowed this quick fix to happen ... and the heat gun setting all of the plastic of course. At the end of the summer season, I'll do the keel soundly ... properly. Although the keel had been well coated by the owner, it had not been faired, worth squat. That was fixed.






    Warren.
    Last edited by Wild Wassa; 08-16-2006 at 06:54 PM.

  14. #14
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    Attention to detail for a keel in progress. If she is a swinger, test everything. Then measure and cut. I notice on a few of the boats that I've worked on, chunks of fairing are missing from badly fitting hardware. A Dremel with a grinding bit will even out the curved shapes on this keel, then the curves will be concentric.





    There is little point going to all the trouble of a finely faired swinger, unless inside the slot is just as smooth as the finished keel. Fairing inside the slot is often overlooked, I notice.





    Both of these photos are works in progress and neither image shows a fine finish yet. I've stopped working on the boat until the second week of next month, to allow for more shrinking of the epoxy with compression strength fillers added. Now that the warm weather is coming, shrinking will happen abruptly.

    Warren.
    Last edited by Wild Wassa; 08-16-2006 at 06:47 PM.

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