1984 Hunter 31 - Cast Iron Keel Rust

[anelso29]

Hello everyone,

I have posted on these forum a couple of times. I am a very new sailboat owner and I am trying to learn as much as I can, so please forgive any ignorance about this topic I have. I'm seeking some advice regarding the cast iron keel of my 1984 Hunter 31 Sailboat. I noticed some rust accumulating on the keel during the off-season, and I'm wondering if it's something that needs to be serviced before placing the boat back in the water.

I've attached some pictures of the rust for your reference. As you can see, there are some areas where the rust has built up quite a bit. The rest of the keel seems to be in good condition, but I'm not sure if the rust is indicative of a bigger problem that needs to be addressed. For full context, last summer I stripped the entire keel down to the cast iron and removed all the rust I could find. I covered the keel in antitrust (then cleaned it off based on the instructions I was provided by the product I used) and I sealed the entire keel in a thick layer of epoxy.

If this is something I have to address again, I am not in a marina where I can do the work myself, I would have to move the boat to another yard first. I would appreciate any insights or recommendations you may have on how to proceed. Should I sand down the rust and repaint the keel, or is it something that can be left as is? I'm also curious to know if anyone has experienced similar issues with their sailboat keels and how they addressed them.

Thank you in advance for your help. I look forward to hearing your thoughts.

 

[Ralph Johnstone]

I covered the keel in antitrust (then cleaned it off based on the instructions I was provided by the product I used) and I sealed the entire keel in a thick layer of epoxy.

Do you still have the instructions for the antirust you applied ? If not, supply a Google link to the product. I wonder if that's where your problem with the lack of adhesion started ? Epoxy usually sticks like to a blanket. What was the brand of epoxy ?

Also, any further info on what happened after the antirust. Was the keel dry ? Any other sources of contamination ?

 

[anelso29]

Do you still have the instructions for the antirust you applied ? If not, supply a Google link to the product. I wonder if that's where your problem with the lack of adhesion started ? Epoxy usually sticks like to a blanket. What was the brand of epoxy ?

Also, any further info on what happened after the antirust. Was the keel dry ? Any other sources of contamination ?

Ralph,

Thank you for your response. Unfortunately, I do not have the specific name of the antirust product that I used. It was a yellow spray bottle with a very strong and unpleasant odor. I tried doing a Google search, but I couldn't find the exact product. I do remember purchasing it from a local hardware store(I know that is not helpful here I am sorry).

Regarding the epoxy, I used the WEST System 105 Epoxy Resin with 205 hardener, which was recommended to me by a seasoned boatyard repairman who has worked on many boats. I applied 4-5 coats over the course of two days. I made sure the prior layer was DRY before applying another layer. I started applying the epoxy one day after using the antirust product. It was a hot and dry day in July when I started applying the epoxy to the keel. Since this was my first time doing this, I dont know if there was any type of contamination.

 

[Crazy Dave Condon]

Look under archives as much has been discussed on this matter. In two weeks and you need my input, I will be glad to discuss this with you.

 

[shemandr]

Welcome to the forum!
When Crazy Dave Speaks - people listen. So, I'm hesitant to add anything except it looks to me that a spot treatment would be inadequate. But you should understand why your good hard work failed (Sorry if that hurts). I'm looking at the anti-rust product.

 

[Ralph Johnstone]

Do you remember, as best you can, exactly what you did after the anti rust was applied ? West System appears to be suitable for ferrous metals so I presume that's not your problem. Actually, pretty well all epoxy compounds are founded on similar chemistry.

I do not understand the underlined section. Contact West System to see if they can clarify and/or offer any further information on bonding to cast iron. See bottom of their page for a phone number and talk their heads off :

It's how they advertise. Check this same page for bonding as well:

Surface Preparation | WEST SYSTEM Epoxy

Learn more regarding epoxy surface preparation and how it's essential to the success of the epoxy application.

www.westsystem.com

I got 2 nickels, a dime, and a ball of lint in my pocket that says West System is going to agree that the anti rust compound was the problem.

 

[Davidasailor26]

The good news is there's still lots of iron left, so if you can't do anything about it this winter it won't be the end of the world.

It is surprising that so much came back after just a year. That might be a failure of adhesion because of the anti-rust product, or something about the epoxy itself. One thing I noticed is where you said you waited for each layer to be dry before applying the next, applying 4-5 coats over 2 days. That might not have been a good curing and re-coat process for epoxy. If the epoxy was actually cured between coats (which I expect it probably was at least for the coat after the overnight) you should clean it with soapy water to remove any amine blush, then sand to make a good key for the next coat. If applying before the previous coat is fully cured (likely what was happening during the day) you can just go straight over the first coat, but it would still feel a little tacky, not "dry".

My preference is to use Interlux Interprotect for the keel. Each year I get a couple rusty spots. I sand them to bare metal, clean, and quickly apply a first coat of Interlux. More coats can follow any time after the first one cures. Antifouling is applied to the last coat while it's still curing (hard enough to leave a fingerprint but not transfer onto your finger). With that approach I haven't had any problems of spots recurring. Some people use an extra step of a phosphoric acid rust converter before the epoxy. That's probably a good measure but not one I've tried. The Interprotect has an extra filler that helps it build up more quickly and might be the reason it's more effective than the neat epoxy you used.

 

[Ralph Johnstone]

One thing I noticed is where you said you waited for each layer to be dry before applying the next, applying 4-5 coats over 2 days. That might not have been a good curing and re-coat process for epoxy.

Very true. Each coat should be applied when the previous coat is still tacky until all coats are applied. Even if this means getting up at 03:00 and applying to avoid a sanding job and inferior mechanical bonding. Your previous partial curing times will dictate the frequency of application. Ask West System about this when you talk to them.

My preference is to use Interlux Interprotect for the keel. Each year I get a couple rusty spots. I sand them to bare metal, clean, and quickly apply a first coat of Interlux.

And there's a completely different product:

No problem with timing for hot coating. Anytime is good.

Thoroughly research each brand of epoxy (Interprotect is also an epoxy) on line USING ONLY THE MANUFACTURER'S INFORMATION. Do not accept/use any information "from other sources" as you have a big project in front of you and the last one didn't work out so well so make this one count. Consider doubling up on the thickness of the coat because :

Each year I get a couple rusty spots.

I don't think that should be happening.

After you have a complete understanding of the product, phone them to discuss any questions you may have. See what they think about a double thickness of Interprotect.

 

[Ralph Johnstone]

If you used this stuff or any product similar to it :

............ that is definitely your problem. I've seen it in use and it turns rust (ferric and ferrous oxide) into a hard black crust. Solid enough material but just not iron.

As the West instructions say, you should remove all the surface material before getting into using an angle grinder with a heavy grit. This avoids grinding the material into the surface of the CI as a molecular film if that's even possible. Ask the manufacturers what they recommend for a top cleaning job before painting.

 

[Davidasailor26]

I don't think that should be happening.

Just to be clear, the new spots I get always appear to actually be in new locations, not places I’ve treated with Interprotect. To treat these few spots per year is not too time consuming, but if they were recurring that would be more frustrating.

 

[Ralph Johnstone]

Just to be clear, the new spots I get always appear to actually be in new locations, not places I’ve treated with Interprotect.

OK, let me back up here to :

I take it you didn't, at some time, strip your keel and paint the whole thing with Interprotect ? If not, isn't it a little expensive to fully haul your boat for rust spot repairs as opposed to an inspection lift and do the keel once and for all and be done with it ?

That's about $275 US for an inspection lift as opposed to $458 US for a full haulout. Maybe your costs are different from ours ?

Mind you, one other item which may negate this entire conversation is that I did a full haulout for bottom painting once in the last 7 years. This time I'm going for one full haulout for bottom painting in 10 years.
If you are bottom painting every 2 years, do the rust spots at that time and :

 

[anelso29]

Thank you eveyrone for your feedback on this topic. Your insights, experiences, and perspectives have been incredibly helpful and have given me a lot to think about.

I am truly impressed by the level of knowledge and expertise that this community possesses, and I feel fortunate to be a part of it. Your generosity in sharing your time and expertise is greatly appreciated.

I obviously have some work to do. Going to get working on it this week.

 

[BigEasy]

isn't it a little expensive to fully haul your boat for rust spot repairs as opposed to an inspection lift and do the keel once and for all and be done

I also spot treat rust spots with interprotect on an as needed basis. I do not haul out for rust on keel only. Usually haul on 3 - 4 year schedule for misc repairs, bottom paint, compound & wax.
On my previous boat ,approximately 20 years ago, rust was extensive and I had the keel sandblasted and I recoated it with coal tar epoxy. Held up well. I have always been told that once the rust has been entirely removed, the coating needs to be applied immediately because reoxidation occurs quickly and interferes with adhesion of the coating.

 

[Davidasailor26]

OK, let me back up here to :View attachment 213344

I take it you didn't, at some time, strip your keel and paint the whole thing with Interprotect ? If not, isn't it a little expensive to fully haul your boat for rust spot repairs as opposed to an inspection lift and do the keel once and for all and be done with it ?
View attachment 213345

That's about $275 US for an inspection lift as opposed to $458 US for a full haulout. Maybe your costs are different from ours ?

Mind you, one other item which may negate this entire conversation is that I did a full haulout for bottom painting once in the last 7 years. This time I'm going for one full haulout for bottom painting in 10 years.
If you are bottom painting every 2 years, do the rust spots at that time and :

View attachment 213346​

The culture in the northeast and northern mid-Atlantic is a little different than the PNW in this respect. We, along with probably 80% of the boats in our area, haul out annually for winter storage. Our insurance even specifies that the boat shall be “laid up” from 11/15 to 4/1, and haul-out is built into the cost of our annual marina contract. Since the boat is hauled anyway it’s common to use that time in the winter and early spring to wax topsides, and lightly sand and repaint the bottom. So hitting the couple rusty spots as they pop up is a more convenient way to handle the problem than blasting and rebuilding the coating all at once. The OP’s coating seems to have failed a little more comprehensively than whatever Beneteau did with my keel originally, so for him another start from scratch might be worth considering.

I see the OP is based just a few miles further south on the Chesapeake than me, so I presume the culture there is about the same as what I’m used to.

 

[Ralph Johnstone]

We, along with probably 80% of the boats in our area, haul out annually for winter storage. Our insurance even specifies that the boat shall be “laid up” from 11/15 to 4/1, and haul-out is built into the cost of our annual marina contract.

WOW, a whole new world of which I knew nothing. Yes, I see your procedure now as easier than blasting the whole thing in one prolonged, backbreaking ordeal.

 

[Ralph Johnstone]

I recoated it with coal tar epoxy.

Damn, I have seen coal tar epoxy used in some gawd awful places and it just will not let go, ever. Mind you, it's near impossible to remove should you ever be so inclined. The stuff I had seen was by Interlux. I have often wondered if that stuff has any place on boats below the water line ? If it didn't work, you'd have to throw the boat away as there's no way of removing it. It never hardens to the point of being able to grind or sand it off.

 

[BigEasy]

Damn, I have seen coal tar epoxy used in some gawd awful places and it just will not let go, ever. Mind you, it's near impossible to remove should you ever be so inclined. The stuff I had seen was by Interlux. I have often wondered if that stuff has any place on boats below the water line ?

Twenty something years ago, coal tar epoxy was commonly used by boat yards & DIYers on keels as well as other underwater appendages. Seems that 15 - 20 years ago there was a shift to interlux 2000 / inter protect, after it appeared on the market. Thats what I presently use. Not 100% sure; however, I believe that Beneteau used interlux to initially coat all of the steel keels.

 

[Ralph Johnstone]

Not 100% sure; however, I believe that Beneteau used interlux to initially coat all of the steel keels.

Rest assured, somebody made an extra buck off that move.

 

[rgranger]

Like others have said, I would spot treat. Grind out the rust spots with an angle grinder..hit it with some barrier coat put some bottom paint on it …10 years of annual spot treating won’t even come close to the labor it would take to restrip and do it all over again

 

[Ralph Johnstone]

10 years of annual spot treating won’t even come close to the labor it would take to restrip and do it all over again

Except the OP may have introduced some bad "ju ju" or "hoodoo" on to the surface of the keel when he cleaned the keel with antirust.

Only time, and the flipping of a few coins will tell which is easier (and cheaper).