Mooring Chain

[KeithH]

The 2003 booklet from Chichester Harbour Conservency Board has a short section on mooring, and mooring chains. It mentions, in passing, that a common mistake is to use galvanised chains for attaching to a mooring.

Can anyone explain why galvanising is not appropriate for this application? I would have thought that it would be - at worst - ineffective, but the article implies that it is "worse than useless". The use of galvanised shackles is specifically mentioned as a bad practice.

KeithH

 

[qsiv]

Two issues spring to mind -
A - you would have a large anode courtesy of the zinc
B - you wont get the oxide layer forming underwater.

Certainly my father would never allow galvanised chains when he was a harbour master.

 

[Trevor_swfyc]

I expect it is environmental, nobody wants zinc in their cockles & winkles. Although we are allowed the use of zinc anodes.
In any case the galvanised surface would soon be erroded off.
Trevor

 

[hylas]

This is a very interesting point and I would also be very interested to learn:

1° ) - why galvanised chains are a mistake?

2°) - what should we use to connect the concrete block and the Mooring buoy??

 

[vyv_cox]

With my metallurgist's hat on, I have been struggling to think of any reason why galvanised chain should be in any way inferior to non-galvanised. So far without success. Ground chain and risers are, in my experience, not galvanised simply on the basis of cost, although all the swivels I ever saw were galvanised. Many mooring contractors cast in a zinc anode at the connecting joint between the two. The pick-up chain is normally galvanised to avoid dripping rust over the decks. Where shackles are used I think it would be difficult to buy a carbon steel one that is not galvanised. Personally I prefer to weld everything with overlapping links, but that's another question.

My own knowledge, and a few searches I have done on the Internet, suggest that galvanising will always provide improved corrosion resistance to steel in seawater. So is there some other reason, not connected to corrosion? The only drawback to zinc coatings that I know of is that it sparks and can ignite gas mixtures. Hardly a problem under water!

I, too, will be most interested to hear the answer.

 

[Mirelle]

I am also scratching my head about this. I once worked for a company which bought a ship which, most unusually, had been zinc sprayed externally all over; we had to blast off the zinc below the w/l as the antifouling paint would not adhere to it, but that is not a problem on mooring chain.

 

[seaesta]

Sounds like some old geezer's ill founded prujudice.

Why not write to the harbour commissioners telling them that you have had advice from an "environmental consultant" (me!) that galvanised chain would be better for the environment and ask them to justify their ban. That should get the buggers moving!! (hope i never need a mooring in Chicester!)
Martin

 

[charles_reed]

Why not write and ask them - they may have a genuine reason - if not they're probably in breach of their duty of care and open to legal action by those owners whose insurance claims are repudiated when their vessels break their moorings.

 

[longjohnsilver]

I have used both types of chain on my mooring and the galvanised definitely lasts longer.

Mebbe someone in the harbour authority does a good trade in non galvanised chain?

 

[charles_reed]

Cynic... nm

nm

 

[Guest]

Invitation ....

I have invited John Davies to answer .... as he is 'boss' of said Harbour Board. It will be interesting for all to see why this has been adopted in Chichester.
Please note that I do not judge either side on this and await response from Chichester ....

Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[SteveA]

Re: Invitation ....

I too have used both types of chain on my mooring and have found that the galvo'd last twice as long.

 

[brian_neale]

Re: Invitation ....

My old sailing club always used galvanised chain, as I remember, and the main point to watch was never to use any stainless shackles or other components under water. The biggest problem (after the owners who used to moor using bits of old sheet, of course) was making sure that shackles did not come undone. I used to take a big hammer with me at mooring renewal time, and mushroom the hell out of the end of the shackle pins once tightened. Needed a hacksaw to remove them again, but at least galvanised shackles are relatively cheap! I used to give the shackle a little squeeze in a vice before hand to close it up a bit, to make sure that there was some pin protruding once tight.

 

[Guest]

Chichester Reply :>

I take the liberty here of pasting the reply from Chichester Conservancy ref. the mooring chain issue. They could not do it themselves - as their ISP is having difficulties and they cannot access the forums. So this is their answer and please .... I wish to point out I do not claim I agree or disagree ......
>>>>>>>>>>>>>>>>>>>>>
5 February 2003


Dear Mr Luther

Galvanised chain in mooring systems

Thank you for your email reference above. I am afraid that we do not have a metallurgist on the staff and the article in the harbour news is based on empirical knowledge, in which we are rich, rather than science.

It is our experience that galvanised chain used underwater as part of a mooring system adds an element of uncertainty to the life expectancy and integrity of the mooring. It appears to us that as the galvanised layer starts to wear a galvanic reaction is set up between the steel and its galvanised coating, causing the links to pit and weaken. This tends to happen to a lesser extent with a self-coloured chain and the rate of wear and therefore its integrity is easier to predict. This phenomena is not displayed equally in all mooring situations; in some drying moorings in soft mud it may be minimal or non existent, whereas on another deeper water mooring it may be quite marked.

It is often assumed that buying galvanised chain is better and our article aims to redress this expectation as on balance in most situations we would recommend a self-coloured chain. I would not draw the implication that it is, “worse than useless,” in many situations it would be perfectly adequate, but when giving general advice covering a variety of mooring scenario’s we do not recommend galvanised chain.

We have found that a small amount of galvanising in the system is particularly bad, such as a galvanised shackle joining two lengths of self coloured chain, this inevitably speeds the galvanic reaction and could be placed in the worse than useless category.

Thank you for bringing the article to our attention; unfortunately we are experiencing difficulties with our Internet provider and are currently unable to access the PBO site. I am not sure if it is coincidence, but PBO are currently preparing an article on moorings and have just visited us to examine some of our mooring practices!

Yours sincerely

Richard Craven
Deputy Harbour Master
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

All I will add is that mixing galvanized with other - such as mild steel or stainless is not a very good idea etc.

Nigel L


Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[KeithH]

I would like to thank everyone for their replies on this subject. I am amazed with the speed and quality of the replies on most sailing issues.

This forum is certainly very effective at finding out information.

Regards

KeithH