Rusty Keel Bolts - How far do I go??

Richard10002

Richard10002

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For various reasons my keel bolts, (14 of them), have been sat in water in the bilge for the best part of 3 or 4 years and have rusted quite badly. I'm close to solving the problem/s of water in the bilge, and am now cleaning up the bolts.

here are 2 pictures of 3 bolts before I started the job:

IMG_0034.jpg


IMG_0035.jpg


I have chipped of as much of the bubbling rust as I can get at, then used a drill with a rotary brass wire brush to get at what I can, then a coating of 10% oxalic acid left for 18 hours, and this is the result on two of the bolts:

keel4.jpg


This is a bolt after chipping off the rust, but before wire brushing and oxalic acid:

keel3.jpg


my plan is to coat the bolts in some rust converting stuff, but wonder if I need to get them cleaner and all the little bits of crap and rust off before doing so.

My further plan was to try and keep the bilges dry, and not coat the bolts in anything, (I think they were painted previously).

Any suggestions welcomed.

Richard
 
The ones on my Moody 31 looked like that. The surveyor said to get them back to shiny metal and then paint them with red oxide bare metal primer and one coat of underwater primer. This apparently still enables you to see any corrosion taking place.

I did all that but still get water in the bilges that is having a slight affect.

I'm not sure if rust converter is useful in this situation.
 
There is a long article in the MOA Library. Wire brushing and Hammerite / gelwash seem to figure on most peoples winter lists. I would not leave them unpainted, it will at leact slow down the process.
 
You have done a nice job cleaning up those bolts!
I would be inclined to paint them with a cold galvanising paint now - the type that is almost 100% zinc, and slather it on lavishly. The paint will effectively then work in the same way as an anode on the bottom of the hull - if there is water in the bilge.
If the bilge is dry - even better!
 
My keel bolt nuts had corroded due to water collecting in the bilges just before I bought the boat. They were originally glassed in but minor cracks had started letting water in and as the rust expanded the fibreglass cracked even more.

Mine were worse than yours and when undone they brought the studs out with them. The very tops of the studs were also corroded so I replaced the whole lot. You may have already done this, but make sure the nuts still have the same amount of useful metal left that they had when new and that the tops of the studs just below the nuts haven’t lost some of their strength due to corrosion.

I sealed the new nuts/studs with several coats of the very cheap (white spirit based) car body underseal. This stuff is supposed to ‘self-heal’ if it gets chipped by stones which I thought was a useful property. Don’t use the more modern waxy stuff – it never seems to dry fully.

Eleven years and two insurance surveys later there are no signs of any rust.
 
[ QUOTE ]
You have done a nice job cleaning up those bolts!
I would be inclined to paint them with a cold galvanising paint now - the type that is almost 100% zinc, and slather it on lavishly. The paint will effectively then work in the same way as an anode on the bottom of the hull - if there is water in the bilge.
If the bilge is dry - even better!

[/ QUOTE ]

Thanks for the compliment, but I've only done 3 out of 14, so there's a way to go, and it's not the most exciting or interesting of jobs! I think a couple a week is the way to go and, whilst I should probably tackle the most awkward ones first, I probably wont /forums/images/graemlins/smile.gif

Cold galvanising paint means nothing to me - will I find a tin which says just that on it, or will I have to read between the lines?

presumably you meant that the zinc will corrode rather than the bolt when it comes into contact with water?

Dont like the idea of coating in gelcoat - I think I want to see what's going on.

Convinced I wont get them back to shiny metal - there aren't enough hours in a day /forums/images/graemlins/smile.gif

Cheers

Richard
 
3 down, 11 to go.......
I would agree that there are always more interesting jobs that can be done, or need doing!
Maybe set yourself a target of 1 per week?

Re cold galvanising paint, if you get the paint on stuff it should say that on the tin. I use CRC Instant Cold Galvanise which comes in a spray can - works brilliantly. I have used it on our shaft coupling, on my very motley collection of rusty spanners, in fact anything that is rusty and which is difficult to get back to shiny metal.
 
Rust converters are fine for some things but however hard you try, you are not going to be able to guarantee totally dry bilges all year round and you don't want to have to take emergency action just because you've got a bit of a weep somewhere - so they do need to be protected.

I've had similar problems over the years and second Bajan's solution. Clean them up as you did the first ones and then spray or paint with zinc. I can't buy zinc paint round here in Spain but zinc spray is easy to buy. I sprayed the end couple of metres of anchor chain in Feb and is is still fine after being at anchor a fair bit over the summer. Cheap, easy to apply, easy to understand (cathodic protection), and effective.

Really nice job you've done there - very professional.
 
Granted. Very amateurish /forums/images/graemlins/wink.gif
 
You may have to read up on the application of Zinc paint protection, too thin will provide long term protection, too thick it will mud crack and still rust.

I seem to recall a figure of 70 to 95 microns, but no doubt someone will give you the correct answer.

Avagoodweekend
 
You must pull out at least one bolt to find out how rusty/corroded the section is that you can't see.
Remember it will cost less today than in the future if your keel comes loose or even worse, drops off.
 
I've read a few things on keel bolts from Moody Owners and those who have removed the bolts have said it was a waste of time.... the rust is just surface rust and they would have been as well to just clean the bolt heads and coat them in something.

Apparently, they are mild steel rather than Stainless Steel for a reason.

I'm not going to pull a bolt unless something suggests it's necessary, and the rusty heads isnt the thing.
 
Not just stainless. I dropped the bolts off a forty year old bilge keeler - a whole heap easier than a fin keelers bolts, but still not easy. Most of them were as good as the day they went in, but several had allowed water past them - just a trace weep - which was why I did the job, and had wasted away across the joint where the water had reached them. One had gone altogether, another was little more than a rusty wire at the worst point, and others had lost up to 70% of their thickness.

They all looked the same from above and below - quite good. there was no way of telling, as with all but the worst where the remnant sheared instead of releasing the nut, they all looked good and allowed the nuts to spin off without too much difficulty.
 
Good job so far but don't stop there. Get a good fitting spanner and remove at least one nut to see the condition of the thread. If possible lock two new nuts together on at least one stud and withdraw to see condition of stud. If you find you are applying a high torque to the stud and it won't shift (and doesn't break) you can perhaps assume that it is sound and leave it but it's best to get at least one out. Someone else suggested they are mild steel. I doubt it. They will almost certainly be high tensile carbon steel so if you rep.lace them get an equivalent. More than likely they will be OK but if you get the nuts off you can clean up the threads and fit new washers and nuts to ensure the threads themselves are sound.
 
[ QUOTE ]
Someone else suggested they are mild steel. I doubt it. They will almost certainly be high tensile carbon steel so if you rep.lace them get an equivalent.

[/ QUOTE ]

From moa technical library:

"This rust problem causes people to ask why Moody use mild steel rather than stainless steel for the studs and nuts, but it seems that there are good reasons for this:



Q: I understand that mild steel studs are not a “cheap“ option for cast iron keels – certainly when one was drawn for survey 5 years ago it was only the top that had superficial rusting.



A: The technical details escape me but I believe that stainless keel bolts are not a good idea. No doubt some metallurgist in the MOA will correct me but I believe it is something to do with the encapsulation and therefore lack of oxygen which can cause s/s to fail. The rust on mild steel keel bolts is aesthetically unpleasant but largely self limiting once the outer layers have oxidised/rusted. [David Tomlinson]



A: I was told by David Moody that the mild steel bolts are better. I cannot remember his explanation, but do remember his saying that they have never had one fall off. I am sure that mild rather than stainless is not for cost saving. [Michael Lucas]



A: I understand the problem is that the type of corrosion SS undergoes with a lack of oxygen makes it subject to catastrophic failure. I think it is also very difficult to actually detect, unlike rust. [Richard Barker]



A: Stainless steel needs a constant source of oxygen to remain protected and this comes from air or water. But put stainless in an environment where there is no oxygen flow and it (a) can corrode (rust or white chalky deposits) or (b) suffer crevice corrosion with consequent weakness. It's significant that the Navy won't have the stuff on its submarines any more! [David Berry]"

It was the David Moody reference that convinced me.... I'm presuming he is of the Moody boats family.

Richard
 
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