Mooring chain rusting

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I have been servicing the moorings at St lawrence Bay on the River Blackwater for about 16 years. The ground chain we use is 19 mm & lasts at least 3 years.Above this we have 5 metres of 25mm multiplaite then 1,5metres of 16mm chain.
Most owners lift their moorings on a 3 or 4 year cycle depending on size of boat.
Each year our work boat is used to raise a length of the mooring to check the top chain, the thimbles on the multiplait & change the top shackles to the buoy if necessary.
If they are all Ok it has been assumed that the chain at a deeper level is of better condition. This has always been so & is probably due to being in the mud & away from light & less oxygen etc..
This year, due to loosing our old tug services we had to employ a tug from the Crouch. This meant that we had to raise all the moorings in one go.
To our surprise & for the first time ever, we found that the chain at the bottom by the sinkers has deteriorated far quicker than that of the upper levels. So much so that a lot of moorings snapped & we lost the sinkers ( 11 out of 42) many due to poor chain.

This can only be due to something in the surface of the seabed. A chemical perhaps, leaching out from the land further up river.
Has anyone else noticed this phenomenon in the area?
If I wanted to bring this to the attention of conservationists - who would I write to & where? Does anyone know who the correct government agency might be who might have an interest in this & where to write with my concerns?It would, of course need others to have noticed the same issue.
 
would be v surprised if your theory is correct - what is going to leach out and only affect mooring chains? The introduction of any chemicals capable of affecting chain would have impacted on the fish etc quite quickly and be noticed.
 
Is there any common feature or correlation about the chain: e.g. different supply that is now affecting risers that had worn more than another supply.
 
I'm a member at Marconi - just up river from you by the sound of it. We lift our deep water moorings every year and have found that electrolytic action is the culprit in many chain problems. We ask all members to put anodes in their ground tackle - because where there are a number of different metals (chain, shackles, swivels etc) the current will flow. The thread on shackle pins is particularly weak - we recommend a tap-weld to secure, or a good seizing.
Could the problems be electrolytic in nature, or is it pure wearing of links (which would imply far more movement than you'd expect)?
Your suspected chemical cause sounds unlikely to me, I have to say.
 
Marmalade said:
I'm a member at Marconi - just up river from you by the sound of it. We lift our deep water moorings every year and have found that electrolytic action is the culprit in many chain problems. We ask all members to put anodes in their ground tackle - because where there are a number of different metals (chain, shackles, swivels etc) the current will flow. The thread on shackle pins is particularly weak - we recommend a tap-weld to secure, or a good seizing.
Could the problems be electrolytic in nature, or is it pure wearing of links (which would imply far more movement than you'd expect)?
Your suspected chemical cause sounds unlikely to me, I have to say.
Click to expand...

If there was electrolytic action it would work right up the chain (or so I would expect)
We have used the same system for many years & it has always been the same
Odd but we do not have problems with pins in shackles ( except idiots who do not fasten the penants to the buoys correctly & so send their boats down to you to recover for us !!!!!!!!)

As an example It has been found that stainless steel chain does not last as long in the Crouch. This is due to the soil structure further up the river. having elements that affect the steel
Is it possible that a section of sea bed & hence different soil structure has been exposed due to erosion etc
 
Last edited:
RivalRedwing said:
would be v surprised if your theory is correct - what is going to leach out and only affect mooring chains? The introduction of any chemicals capable of affecting chain would have impacted on the fish etc quite quickly and be noticed.
Click to expand...

,
Possibly , but has anybody commented or brought it to the notice of the relevant agency- whoever that may be?
 
I am also a Marconi member and have found that your past experience is the same as mine, chain nearer the anchors lasts longer than that near the riser. I had to end for end mine last year to get one more year out of it. This year we are going to start a three year laying programme with annual inspections instead of taking up every mooring each year. I will pass on your observations to the guy in charge of moorings.
 
From Daydream Believer:

As an example It has been found that stainless steel chain does not last as long in the Crouch. This is due to the soil structure further up the river. having elements that affect the steel
Is it possible that a section of sea bed & hence different soil structure has been exposed due to erosion etc.

I think this is almost certainly the case if there is an issue. Wholly natural, last year's easterlies, up catchment runoff etc.. Its a dynamic environment.
 
a popular choice at the moment seems to be the rope riser - traditional ground tackle on the riverbed (chain and 2 anchors for us) with a rope riser made using modern rope with a load rating easily as strong as the chain it replaces. But are we just swapping problems? Rope (even very strong rope) is subject to chafe whereas chain is impervious.
 
Chalk said:
From Daydream Believer:

As an example It has been found that stainless steel chain does not last as long in the Crouch. This is due to the soil structure further up the river. having elements that affect the steel
Is it possible that a section of sea bed & hence different soil structure has been exposed due to erosion etc.
.
Click to expand...

The three eyed fish that have been irradiated by Bradwell Power Station need more iron in their diet so they nibble on the chains and cause them to degrade more quickly. the worms in the mud also need more iron in their diet so they nibble on them as well.
 
We have used a 25mm* 5 M length of multiplait in the the riser for the last 35 years & this can last for over 15 years if we change the nylon thimbles every 3 years. However, we design it so that it does not lay on the seabed too much. We also have 7-8 M of 19mm chain under it to give some catinery action.One does not get this with all rope effect. Above it we have 1.5 M of 16mm chain to keep it below prop level when motoring off.
Last year we lost a boat because the new all 38mm polystell rope mooring wrapped around the keel which cut it like a knife through butter in wind over tide situation.
We did originally intend changing but also found that the edge of the large thimbles we used cut the polystell rope if it could not flex across the mooring sinker properly. ie it needs to flop over in line with the rope otherwise if the thimble catches on the sinker it acts as a knife right where the splice starts.
If we could prevent this, we would threadle some large chain links on to the rope at 1/3 & 2/3 depth to make sure the rope sank properly. Trouble is that without chain risers the boats veer about more & are more liable to tangle in the rope & cut it.
We do not recommend boats above Drascombe size until we have more feedback on how polystell performs long term

We also get the odd, idiot, fishing boat, trawling right through our moorings, in the winter, which can cause chaos & abrade some ropes
 
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