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Old 07-01-2018, 11:00   #1
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Coating keel nuts/bolts?

Please forgive me, but I feel I need a little set-up before I ask my question.

I recently was presented a 1974 Newport 27 as a project boat to reestablish and build up my maritime skill set before I get my final boat and retire by the sea.

As part of the process, I've been working on the lead ballast on my boat. As is common, the ballast is buried in a combination of GRP and fairing compound in a false keel, most of which has suffered delamination from the lead due to water seeping down from the bilge. Suffice it to say it's easy to get the coating off. Along with removing that outside cover, I've stripped the resin covering the keel bolts and nuts from the bilge to do repairs and to prevent any further water damage. As expected, the nuts are in rough shape. That said, Im not absolutely sure yet that I'll have to drop the ballast and replace the bolts. The boat has only been used in fresh water, or what passes for it in Lake Michigan near Chicago, so the bolts haven't been exposed to much if any chlorides. I'll know more a little further into that aspect of my project.

Which brings me to my question; Why would I replace the resin in the bilge, or for that matter, even want to coat the stainless steel hardware in the bilge? My understanding of stainless steel is as long as you select the the correct alloy for the enviroment, like 307L or 18-8 for salt water exposure, you should allow the metal exposure to oxygen so it can form a microscopic layer of protective oxides. Putting stainless steel in a wet, anaerobic environment with chorides/nitrides/sulfides present will result in the steel developing micro-fractures due to corrosion, increase the chance of stress fractures, and allow it to corrode more like carbon steel. Am I wrong here?

What's your experience in this matter?
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Old 07-01-2018, 14:14   #2
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Re: Coating keel nuts/bolts?

In our last two boats, the nuts have been exposed to the air and are easily accessible. No problem with them. Shiny like new. This boat's 28 yrs. old.

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Old 07-01-2018, 16:46   #3
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Re: Coating keel nuts/bolts?

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Originally Posted by JPA Cate View Post
In our last two boats, the nuts have been exposed to the air and are easily accessible. No problem with them. Shiny like new. This boat's 28 yrs. old.

Ann
Ann, what material are/were those bolts?
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Old 07-01-2018, 17:57   #4
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Re: Coating keel nuts/bolts?

All 300 series SS are actually pretty close to each other in strength and corrosion resistance. Close, not identical.
18-8 I believe is just another name for 304 SS.
You are correct the Stainless should be exposed to air all the time, think your rigging for instance, and for the reasons you suspect.
I believe nobody would use 304 SS for thru hulls or seacocks, but we will hold our keels on with it.
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Old 07-01-2018, 18:51   #5
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Re: Coating keel nuts/bolts?

Dropping a keel is a pretty useful learning experience. It's rarely without surprise.

And if the keel has never been dropped, 40 years is past due.

At a minimum torque those bolts to be sure none are broken.

1974 is early for stainless bolts. They could be galvanized or mild steel. If those are stainless bolts the corrosion risk is in the airless area out of sight from inside the boat. And even without corrosion, it would be good to renew the bedding. Keels must mate perfectly - any gaps or flex significantly weaken the structure.

An issue with old stainless bolts in lead is that they can be very hard to remove. One frequent solution is to sister more bolts in beside the existing bolts. If you do this, consider silicon bronze that does not have the crevice corrosion issues.

Here's a pretty good piece about annual keel bolt checking.

http://www.waterlinesystems.com/wp-c.../KeelBolts.pdf
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Old 07-01-2018, 22:27   #6
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Re: Coating keel nuts/bolts?

Thanks to all.

18-8 covers a family of stainless alloys that includes a variety of the 300 series stainless family. The main characteristic is 18% chromium, 8% nickel. If you see an "L" in the designation it mean there is lead in the alloy. 300 series 18-8 is more corrosion resistant than the 400 series family. In my experience 307L and 316L have the best reputation for resistance to corrosion in chloride rich environments. I have access to a machine shop where I can fabricate hardware from raw rod stock if I need to, so if I go with stainless steel, either of those are an option.

Carl, as for what is there now, someone else mentioned they might be galvanized carbon steel. Well, you both were right. I used a magnitometer and got a 25.01 Gauss reading, which is in the range i'd expect for oxidized carbon steel. Further research has told me the keel bolts are embedded 16" to 18" long J-bolts. From what I can tell they have never been accessed, let alone re-torqued. So, it looks like I'm going to have to drop the ballast, do some repairs, install some new keel bolts, then rebed the ballast, yeh!

Fortunately I have fork lifts and a 10-ton bridge crane in my shop with a 25' spreader bar that will make the job significantly easiler.

Just a side note: the surface of the ballast has some significant signs of oxidation and even some major areas of leaching, with pits over 0,269" deep, so while I have it off I'll do some releading to resolve that. That, and the signs of three previous repair attempts tells me this has been a long term problem that no one cared to fix correctly. I really don't have to go that far, but my OCD won't let me leave that alone. Again, my shop has a lot of tools most don't have access to, like sand and slurry blasters, so I'm equipped for the undertaking.

Again, thanks for the input. I usually can rely on my knowledge, but I really like having a sounding board so I don't get arrogant and make mistakes.
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Old 07-01-2018, 22:47   #7
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Re: Coating keel nuts/bolts?

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If you see an "L" in the designation it mean there is lead in the alloy.
Nonsense! L = low carbon steel subtype. So 316L is lower in carbon than 316.
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Old 07-01-2018, 22:51   #8
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Re: Coating keel nuts/bolts?

Alan, that's interesting. My steel supplier's book was where I quoted that from. I guess I'm going to have to have a talk with my rep tomorrow. Thanks.

See, that's why I like a sounding board.
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Old 07-01-2018, 22:57   #9
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Re: Coating keel nuts/bolts?

FYI, I hadn't considered silicon bronze before, but from a quick look at the specs of C655, I'm liking what I see. I'm going to have to look further into that as an option.
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Old 08-01-2018, 02:55   #10
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Re: Coating keel nuts/bolts?

Quote:
Originally Posted by Alan Mighty View Post
Nonsense! L = low carbon steel subtype. So 316L is lower in carbon than 316.
Quote:
... If you see an "L" in the designation it mean there is lead in the alloy. ...
Indeed!
Basically, the "L" stands for “low carbon”. The L means that the carbon is limited to 0.03% maximum, and this make difference when you have to weld it.
Differences between 316 and 316L Stainless Steel | Penn Stainless Products
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Old 08-01-2018, 07:27   #11
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Re: Coating keel nuts/bolts?

There are much better metals than SS for this job.
However maybe a little sanity check is in order, by that I mean she is a 1974 build, and you have said the bolts haven’t ever been touched and are just zinc coated mild steel.
She is 44 yrs old and the bolts have not failed. It’s unlikely she will be around for another 44 years, maybe nothing more than zinc plated mild steel is warrantied?
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Old 08-01-2018, 14:03   #12
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Re: Coating keel nuts/bolts?

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She is 44 yrs old and the bolts have not failed. It’s unlikely she will be around for another 44 years, maybe nothing more than zinc plated mild steel is warrantied?
Good question! And it brings another one up for me: has anyone documented a keel loss due to failed/corroded keel bolts? I can remember several that were due to failure of the structure to which the keel was bolted, and at least one where the bolts pulled out of the lead casting, but none where the keel fell off due to rusted or fatigued keel bolts. Plenty of instances where wasted bolts were detected and removed with great wringing of hands and exclamations of "OMG look how close we were to death", with pix posted on the web. I suppose there must have been cases... anyone remember one?

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Old 08-01-2018, 18:26   #13
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Re: Coating keel nuts/bolts?

Good points about the galvanized bolts. I was talking to shipwright online who is familar with this era GRP boats built in SoCal. To his knowledge there has been no hard proven case where keel feel off one of these boats due to bolt failure. He told me to not over think the repair nor think that I must rely on the keel bolts as the main method of attachment. He seemed to have great faith in the adhesive used to attach the keel. His advise was similar in that if there has been no movement at the keel stub, just cut the nuts off, clean up the threads, replace and torque. If I feel I must, use the "Catalina Smile Solution" method and sister some long lags in between the existing keel bolts. On the otherhand, if there has been movement, then definitely consider dropping the keel and fixing it right.

Also, for anyone who cares, I called my rep at my steel supplier about the info I referred to in a previous post. Turns out they knew about it being wrong and sent out a replace section, which I didn't get. It seems the section was supplied by their "foreign" (read that Chinese or Indian) stainless steel vendor. He also mentioned they had problems with alloys and certs from that vendor, so they no longer use them. Gee, I wonder why.
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