Stainless steel mooring chain

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colbo3765

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does anyone have any views on replacing a galvanised top chain on a mooring with one made from stainless steel? our current top chain has gone rusty in less than a year and leaves nasty streaks down the deck.
 
I thought that the issue was joining stainless to galvanised further down the mooring - they corrode each other. Zinc in the galvanised against chrome in the stainless caused cathodic action.
 
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My understanding is that you either have all stainless (v expensive) or all galvanised......as MoodySabre says, don't mix the two you are asking for problems.
 
Mooring Chain

Ours has a 25mm nylon rope atatched with a loop in the end .. We pick it up , put it over the bow roller and use a mooring line to fasten it to the two front mooring cleats .. Letting go is very sinple .. No damage as its all rope .. The rope has been on a couple of years now and is not in bad shape ..
 
dukes4monny said:
My understanding is that you either have all stainless (v expensive) or all galvanised......as MoodySabre says, don't mix the two you are asking for problems.
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Stainless steel is not rustless. If it is not exposed to oxygen in the air it will corrode. Why do you need to take chain onto the deck? Why not replace the top couple of metres of your riser with nylon?
 
Any stainless should be electrically isolated from any other metal, and if any part of it is under water, an anode is a good idea.
Like exfinnsailor, I favour a good size rope. But I appreciate that chain is better in some circumstances due to chafe!
 
thank you all for your very quick replies. noted on the galvanised-stainless mix. I wouldnt use it under water as I am aware of the galvanic corrosion issues but I wasnt aware of the issue about attaching it to galvanised so thanks. we have quite a heavy boat, nearly 9 tons fully loaded. none of the other boats on our trot use nylon risers so I am thinking, safety in numbers. it does get a bit choppy there wind over tide and the harbour authorities favour top chain rather than nylon but they dont have to pay for topside repairs or make the effort cleaning the rust streaks off of the deck
 
I did this at the start of the season for the same reasons you give, the mooring provider thoughtfully fitted a s/s swivel which I attach to.
If you are going to join s/s to galvanised then a plastic bush on the shackle pin will provide insulation.
The chain dipping in the water is not a problem, crevice corrosion only occurs in anoxic conditions.
 
I would use a thick rope with anti chaff protection but i would also have a slack chain as backup....i would wish to sleep at night!...in a storm....but wots wrong with good galv chain ...that should not rust on top deck?
 
colbo3765 said:
does anyone have any views on replacing a galvanised top chain on a mooring with one made from stainless steel? our current top chain has gone rusty in less than a year and leaves nasty streaks down the deck.
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Had pretty good results using off cuts of plastic thick wall hose inside old fire hose. Boat end sikaflexed to prevent any staining.

Avagoodweekend......:rolleyes:
 
colbo3765 said:
does anyone have any views on replacing a galvanised top chain on a mooring with one made from stainless steel? our current top chain has gone rusty in less than a year and leaves nasty streaks down the deck.
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Not if you want to find your boat there when you come back.

SS has varying grades but all suffer from pitting corrosion underwater. I have first hand experience of SS rudder heel fittings corroding (2 boats) and corrosion on oceanographic instruments that were built of the highest grade ss for submerged use. You will find lots of info on the web including one guy complaining that his all ss anchor chain was corroded in a couple of seasons of cruising use, and the replacement was no better a year later. (Very big expensive yacht and IMO being badly advised by the sales people)

If the problem is rust stains on deck have you considered rope tails so that the chain is only brought in as far as the stem roller, then rope to make fast on deck. Should not chaffe if the chain and roller take the movement. I used this method for many years on a swinging mooring - with two rope tails to different cleats just in case.
 
Evadne said:
crevice corrosion only occurs in anoxic conditions.
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Two points
- crevice corrosion can set up due to slight chemical differences in the ss itself causing localised electrolytic cells. As each chain link is welded chemical differences are inevitable.
- anoxic conditions occur under marine growth creating an electrolytic cell causing corrosion between the oxygenated surface in the water and the anoxic area under the growth - from experience barnacles are especially effective in this way.

It will be interesting to hear how long your chain lasts.
 
Thanks all, I am going to track down top quality 10mm galvanised for a new top chain and have a nylon strop as a snubber. Hopefully that will last more than a year before succumbing to the rust problem.
 
thanks Old Harry, you have just solved it. Our mooring chain is made off on to a stainless steel capstan on deck. It must be a galvanic reaction stripping the chain and leaving it to rust. I will make alternative arrangements.
 
Get rid of steel

This is my current set up in Mexico. 25mm Dynex Dux (breaking strength 80 tons) It is way oversized, but it was a piece the supplier had available. No more worries about steel corrosion, I even lashed the set up together with 5mm Dynex to eliminate shackles ( I did not use the shacles in the photo)........:-)
 
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