Chain life...?

[mdrifter]

In 2006 I bought 60m of 8mm uncalibrated galvanised anchor chain and I'd like to say it has served me well but I really don't think so. It was bought from a British manufacturer who has a hot dip galvaniser close at hand. Having been sailing away from the UK since 2007 and having anchored modestly (I have recorded the exact number of occasions) I have decided to jettison the lot because of the degree of rusting that has occurred in several sections. I don't think it has been stored aboard or ashore in unusual conditions nor has it been used excessively. Perhaps this is a can of worms best left unopened but I'd be interested in other opinions and of course from where should I seek its replacement, please?

 

[VicS]

MM5AHO is the forum's galvaniser. His opinion would be interesting.

He might be able to suggest whether or not you should be thinking about getting it re-galvanised rather than replacing it.
If so he will be able to advise you on how to choose a galvaniser, what processes ( centrifuge ???) the galvaniser should have etc.

 

[duncan99210]

Doesn't look too bad to me. If you're worried about the rust, cut out the affected bit and use galvanized c links to join up the bits.

 

[vyv_cox]

I agree, that doesn't look at all bad. My Italian-made chain had almost no zinc left after three full seasons. The rule of thumb is that a reduction in cross-sectional area of 10% is acceptable, this usually occurs at the intersection of one link with its neighbour. Yours looks to be well within this.

I had my chain regalvanised by BE Wedge in the West Midlands, (and subsequently repeated the process for another boat) and wrote up the experience in YM. There is a page on it on my website http://coxengineering.sharepoint.com/Pages/Regalvanising.aspx Wedge own the only dedicated chain galvanising line in UK. There are many other galvanising plants who will do the job but you run the risk that links will be 'welded' together.

 

[mdrifter]

Perhaps I should post a close up...and/or wire brush the rusty sections and then post! I'm not unusually paranoid about anchoring but I would sleep more easily were it not for the numerous rusty sections. As things look to me there may be more than 10% but measuring is believing. As for cutting out the sections - that might require about 4 links minimum with some loss in strength. After the winter it looks a bit worse than the pic taken last October. Who might supply "good" chain these days if I take the plunge? BTW I contacted Wedge and taking into account a minimum charge of c.£150 for galvanising and c.£90+VAT for carriage...new chain is looming!

 

[doug748]

My prejudice is that Messrs Wedgie and Co will do a better job of galvanising than many original manufacturers. Certainly, I had mine done (not by Wedge, tho in the same area) about 6 years ago and it is still fine.

I also don't think that chain looks too bad. Remember the zinc is slowly rotting away, doing it's job, even if you never take the chain out of the locker. Looking on the bright side, you will get £100, or so, for it if you decide to buy new

 

[William_H]

As said I think that the chain rust problem is purely cosmetic. The chain is very unlikely to part due to wear/rust. As said it is the area of contact one link to another that is the concern on mooring chain. The loss of strength is likely to be in proportion to the loss of cross sectional area of the link. So 10% less in diameter is a lot less than 10% of area.
I would imagine the strength of the chain is vastly greater than tension you would ever put on the chain in anchoring. Indeed probably a lot stronger than the chain attachment on the boat. Just look at it all reasonably. Loss of galvanising is not in itself a problem. good luck olewill

 

[TQA]

I live on the hook for about 360 days a year. usually I get about 5 years from my chain.

The exception was some Italian 10mm x 28 mm which I ditched after 16 months as the galvanizing was gone on much of the chain and it was starting to jump on the gypsy because of wear..

 

[sailaboutvic]

We just had to throw 35 mts of 10mm chain after just two years , the rust was so bad part of the links was rusted together , the original chain now six year old is all most as good as new . I just hope what I replaces it with will last a bit longer

 

[charles_reed]

From the photo, I'd think you should congratulate the supplier on the quality of their galvanising.
A point I will make, my experience is that unused chain stowed in a locker rusts far faster than chain regularly used and stowed on a pallet outside the boat overwinter. The nature of your rusting suggests it's seldom been used and the rusted areas are those lying in water at the bottom of your chain locker.
Cheap galvanised chain starts rusting in 3-4 years, My 12-year old UK-made chain is as good as new, though I did re-galvanise the previous chain and anchor after 10 years.
The 7mm Italian chain I bought for the kedge anchors, showed signs of rust after 5 years.
I'd certainly not ditch the chain, but have it pickled and re-galvanised (about 30% the price of replacing). The only problem is that you need a specialist galvaniser and sufficient weight of chain to make it worth his while putting it through. Most I know now demand at least 250kg.

 

[J Neeves]

Your chain is almost 10 years old now and looks in good condition. Most of the chain in the image looks to have good gal. I'd end for end the chain and have that area of slight corrosion at the bitter end, rather than the anchor end. I think it very unlikely, in the absence of close ups, that you have lost anything near 10% of chain through corrosion and it looks to have a good few years life left in it.

I would be interested to know how many nights you had anchored and why you think you have those 2 short lengths of preferential corrosion - were they, as Charles suggest, at the bottom of the locker, or do you have other ideas.

I did some abrasion tests with a cross section of 16 different gal chains that were almost continuously sweeping a silica sand seabed. The best, after 70 days, still had intact coating, but the coating was very thin. The worst abraded after 30 days - and the loss of gal simply got worse and worse. The test was more severe than normal anchoring, as usually chain does not continuously sweep the seabed, but it is indicative of the variability of gal quality (which reflects some of the above posts).

Jonathan

 

[LadyInBed]

Even if you replaced the chain, it is pot luck that the galvanising on the new chain would be any better or last longer than your current chain!

 

[vyv_cox]

Even if you replaced the chain, it is pot luck that the galvanising on the new chain would be any better or last longer than your current chain!

I would hope you are taking a very pessimistic view! Chain as it comes from the maker is centrifuged to remove as much zinc as possible, saving them money. Batch galvanisers or the Wedge chain line do not do this, resulting in galvanising that is considerably thicker. The link to my website given earlier shows the first chain I had regalvanised. That was about five years ago, since when despite extensive use it looks as good as new. The original galvanising had pretty much disappeared after three years, photos in the same link.

 

[saab96]

60m chain is a lot of weight to keep in one place. If you could shift half of it out of your chain locker you might balance the boat better and keep the (probably) rarely used 20 to 30m in the dry. I wouldn't cut out the rusty parts unless you have lost a lot of metal. I don't like joining links cos as soon as you hammer them into place you have knocked off the zinc and started the rust. If regalvanising makes sure of the centrifuge!! Oh dear, a solid heap of galvanised metal. Have your anchors done to get up to the galvaniser's minimum weight.

 

[dovekie]

Just in case it's helpful, I think 10% loss in diameter is MORE than 10% loss in cross-sectional area, more like 19%, presumably with 19% loss in strength.

As said I think that the chain rust problem is purely cosmetic. The chain is very unlikely to part due to wear/rust. As said it is the area of contact one link to another that is the concern on mooring chain. The loss of strength is likely to be in proportion to the loss of cross sectional area of the link. So 10% less in diameter is a lot less than 10% of area.
I would imagine the strength of the chain is vastly greater than tension you would ever put on the chain in anchoring. Indeed probably a lot stronger than the chain attachment on the boat. Just look at it all reasonably. Loss of galvanising is not in itself a problem. good luck olewill

 

[LadyInBed]

I would hope you are taking a very pessimistic view! Chain as it comes from the maker is centrifuged to remove as much zinc as possible, saving them money. Batch galvanisers or the Wedge chain line do not do this, resulting in galvanising that is considerably thicker. The link to my website given earlier shows the first chain I had regalvanised. That was about five years ago, since when despite extensive use it looks as good as new. The original galvanising had pretty much disappeared after three years, photos in the same link.

That was the point I was trying to make, but didn't quite get round to actually saying it :redface-new:

 

[J Neeves]

A zinc coating on the outside of your chain is not much use, on the assumption you use the chain. It looks pretty in the chandler but it is very, very soft and wears away at an exceedingly fast rate. Consequently you, the owner of the chain, gains no benefit and the galvaniser loses money because zinc is expensive. The Zn/Fe alloys, the beneficial product of galvanising, which underlie the zinc outer coating and 'sit on top' of the original raw steel, are tough, or hard, and are more abrasion resistant than the underlying steel. The alloys protect the steel because they are both hard and offer the galvanic protection. A thick coating might be mostly zinc but even a thick coating of alloy is not always beneficial if it does not adhere to the raw steel - it might flake off, a not uncommon phenomena. Some galvanised product has a good thick layer of alloy but in prioritising thickness a sacrifice can be made to adhesion.

Theoretically the best galvanising should be from chain makers who conduct their own galvanising as they might prioritise both adhesion and thickness. Independent galvanisers might prioritise their major customer base (which might not be chain) and might look to optimise characteristics that are not the most ideal for chain. Knowledgeable and careful galvanisers should be able to alter the process to better suit the product - the technology is hardly new. Many Chinese chain makers are vertically integrated as are Peerless in America with their own galvanising facility.

Jonathan

 

[TQA]

Just to show you what can happen.

This chain was 3 years old. 18 months in daily use then 18 months in my backup locker.

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