Stainless steel anchor chain

[Zing]

316 stainless isn't remotely as good as it looks.

Take care with the selection of materials in your ground tackle, or anywhere on the boat for that matter. Particularly 316 should be avoided where it is taking any substantial load whilst exposed to sea water (or in applications where it may be susceptible to crevice corrosion). A 316 chain might be fine for a boat that only ever anchors in light conditions, but for anyone spending many weeks at anchor in all conditions it is asking for trouble to use such material. The main reason is that 316 suffers stress corrosion cracking at very low stress levels - about 4% of its yield stress level, which is a trigger point you will see in a decent blow at anchor. It will eventually fail in such use, maybe after many years, but it will fail and will do so probably without warning. It will also pit easily and once pitted will self destruct in a relentless, irredeemable process. The good news is you can get a 2205 duplex chain, which has dramatically better resistance to SCC (at 35% of yield) and will pit and suffer crevice corrosion at much higher temperatures. It is still an experimental use for duplex stainless. Better, would be the higher stainless grades, but availability is a major problem. Notwithstanding its superiority to 316, duplex chain is more vulnerable than galvanised steel to all failure modes and a lot more expensive.

Sometimes people have found it necessary to dump the chain on the seabed in an emergency, so not having to throw away your expensive jewellery at such times would be an advantage.

As I do a lot of anchoring, until cheap titanium or high grade duplex comes along I will only use high strength galvanised chain, shackles and anchors.

 

[Neeves]

+1

Succinctly put.

In an earlier post I offered the link to Cromox #5, which has a manufacturer's view. I did not offer your detail and assumed the OP would check the link.

I think you are suggesting you would not even trust Cromox - which means the only option is gal?

 

[Magnum]

Well, I wasn't expecting that. Are you saying my s/s anchor chain upgrade is rubbish?

 

[Hurricane]

Well, I wasn't expecting that. Are you saying my s/s anchor chain upgrade is rubbish?

I think they probably are.
IMO though, you aren't wasting your money on S/S
I have galv but I would probably buy S/S if I were buying again.

OK, S/S might have the problems that they mention but think aboit how you are going to use it.
Do you really want your SWMBO having to kick a pile of galv chain over every 15m during anchor recovery - thats what we have to do.
Imagine you need to leave an anchorage in a hurry - the last thing you want to do is faff around in your chain locker making space for galv chain when s/s would just run smoothly in.

And do you really believe that 12mm s/s chain is just going to break on you?

 

[MapisM]

316 stainless isn't remotely as good as it looks.
...
...
As I do a lot of anchoring, until cheap titanium or high grade duplex comes along I will only use high strength galvanised chain, shackles and anchors.

Blimey, and here I was, having always thought that galvanized everything is the way to go just because it's cheaper and works equally well.....

 

[MapisM]

I think they probably are.
...

All agreed M, BUT!
If your anchor locker is large enough (and IIRC yours is), there's no NEED to kick the chain pile upon recovery.
We also do that, as you probably remember, but not because we MUST - it's just to avoid the risk of having the chain self-tangling upon the next deployment.
In other words, if recovering in a hurry, we can always do it in one go, taking care of the (possibly) tangled chain later. Fwiw, it never happened to us in 16 years with this boat.
Secondly - and in a sense most important, because this applies also to s/steel - the advantage of having swmbo controlling the anchor locker is that she can also rinse everything with fresh water, while she is at that.
The result being that our 2x100m galv chain still is almost as nice as new.
Fwiw, I've seen 3 years old s/steel chains badly corroded - superficial as it might be.

 

[Neeves]

Mapis - rinsing gal with fresh water and the chain locker, as you correctly point out, will extend life of the chain. Specifically get rid of the mud. Opening the hatch to allow free circulation is also advantageous, though maybe it does not look nice. Make sure the chain does not sit in a puddle pf water and that the locker drain is clear. Having the chain sit on a perforated mat (or base) allows the chain to dry out/

Chain lockers almost appear to be designed by chain makers anxious to reduce chain life.

The problems of stainless are well documented, check Mr Google for Crevice Corrosion and Seawater - it will keep you busy all day. Most of us reject stainless not because its expensive and we are all paupers, not because we do not think it beautiful, we do regret that it would match our yachts perfectly but because gal is technically superior. Nearly all gal chain is Proof Tested, batches from Western suppliers are break tested. European, American and Australian gal chain is uniquely marked with a makers mark and is available with a test certificate, free of charge, if you ask - and reports of gal chain failure are noticeable by their absence.

 

[Zing]

Well, I wasn't expecting that. Are you saying my s/s anchor chain upgrade is rubbish?

No, that'd be harsh. If it is really oversized and you just use the anchor as a lunch pick or for bobbing about in a windless Med summer overnight now and then, then no worries about SCC.

I just looked it up and if you follow the usage guides on washing and monitoring such as Cromox put out then you should not suffer pitting or crevice corrosion, but I think you will find that to do that is more trouble than kicking the anchor chain down in the locker. By the way, they do warn buried in the CYA verbiage that whilst their 316 chain is corrosion resistant in freshwater use, it is not corrosion resistant in sea water. They should give that warning in the retailer's blurb in my view.

If you mainly want the nice look of it you could fit a length of stainless chain from the windlass to the anchor. You could oversize it easily with shackles. On deck it will be easier to keep rust free as rain will help, but it will just rust less. It will be no different from rain washed stainless stanchions, which do get corroded without due care.

They may let you change to the duplex chain, that would be much better. Or better still, galv chain.

 

[Magnum]

We will be anchoring overnight frequently in the med. Whilst we would not choose to do so in a blow, we may have no choice if it just happens, which it often does in the med.

I haven't heard any reports of s/s anchor chain failing. Princess have recommended and warrantied it.

 

[Neeves]

If they have warranted the specific chain you have purchased then hopefully they know what they are doing. I find it difficult to believe they will warrant any stainless steel, even any 316 stainless chain.

Much stainless is described as 316 but it varies widely. Much now comes from China and some is excellent, some is absolute rubbish. I tested a Chinese stainless chain it failed well under strength and at the weld (the weld should always be stronger than the chain). I've tested shackles (stamped 316) bought from reputable UK retailers that are grossly under strength and tested shackles (stamped 316) bought in the back streets of Hong Kong that were excellent.

If you have a certificate from a reputable testing agency defining batch number, Proof Test, elongation at break and break strength then you have done more than most. If you are not able to obtain a test certificate - wonder why.

 

[Portofino]

Magmum @post # 28 I asked if you have an anchor wash ?
That important I think if it's done right .

With Galv the demise is it rubbing on the bottom ,sand etc eventually straches off the zinc coating ,thins it down and the steel starts to corrode as its looses it's protection .Either nenew or re galvanise -bearing in mind it most probably has been shock loaded and stretched at some point in its life ,
With Stainless steel it's protection comes from a thin layer of oxidisation on the surface ,that protects it ,like your guard rails ( not that I have them or window frame .Assuming quality here not cheapo stuff?
When SS chain rubs about on the bottom when the boat turns this layer too is rubbed off , thing is its single didgit thickness in microns so comes off in a few hours on a sandy or volcanic bottom .Quality Galv has 100 micron + of Galv to go at .
Lack of suffient oxygen , under water - more so if it's submersed in mud -means oxide layer can not reform quickly enough.
While this protective oxide layer is off seawater finds crevices at a microscopic level -not easily visible to the naked eye --and "crevice corossion " goes unchecked -weakens it ----
So it would help to extend its life (SS) if it's washed with fresh water to rince the salt off ,and stored dry to re oxidise in the air .
At least with Galv -you kinda know visually when it's ready for replacement .

There's also issues surrounding shock loading ,SS has less stretch and more likely to snap .AOTBE !
Hence I can clearly see Neeeves advocating "snubbers " to ease any potential shock loads .

I can see the appeal in boats cosmetically that have chain /anchors on display ,and those with pilling issues with Galv .
How ever a decent anchor wash is the Pink Elephant in the corner .

 

[rwoofer]

Question for Neeves. How long does SS need to be under water for crevice corrosion to really take hold? Is a series of overnight stops enough to do it or are we talking about long term anchoring?

 

[Portofino]

Question for Neeves. How long does SS need to be under water for crevice corrosion to really take hold? Is a series of overnight stops enough to do it or are we talking about long term anchoring?

If its the oxide layer has been abraded off on the sea bed in a few minutes of the boat swaying about .
And--- the chain is stored unwashed soaked in electrolyte -then its happening out of the water as well .
See note 4 ---- needs a wash ,and as allready stated there not happy about "seawater "
With the parts not abraded ie the catenenary part and poss the part secured to the anchor ( enough out to prevent movements) -total submersion as you say in longer term continuous overnighters etc , then eventually the thin oxide layer is too thin in concentrated seawater Med being the most concentrated to protect -so that part starts to corrode .-but has a bit to go to catch up on the abraded part .

Cox engineering has a good diagram on SS crevice corossion .

So we are back to anchor wash ----- for SS --- - as you put it in the locker .
Wash that salt electrolyte off .

Your Galv chain has just lost a fraction of over 100 microns on the abraded bit ,the rest is ok and apart from those visable orange rusty bits when they occur( depending on the thickness and use ) -wet salt deposits are fine on the coating ,so no pressure to wash it every time .You gonna chuck it eventually , semi consumable 5-8 years
See note 4
http://www.cromox.eu/pdf/en/SH_Ankerkette_04_2013_eng.pdf

 

[Magnum]

Magmum @post # 28 I asked if you have an anchor wash ?
That important I think if it's done right .

I can see the appeal in boats cosmetically that have chain /anchors on display ,and those with pilling issues with Galv .
How ever a decent anchor wash is the Pink Elephant in the corner .

Yes we have an anchor wash.

The attraction of s/s chain is nothing to do with appearance but all about flow.

 

[vas]

puzzled to read here that I'm not the only one that has to drop the stack of galv chain in the anchor locker every 30m or so...
That's the sole reason of my contemplating buying a SS10mm chain (to replace my ancient 8mm galv one).
Saw some prices, was shocked and promptly forgot about it.
Then I thought I'll go the other way and search for these fancy chain spreading kits that fit under the deck hole smoothly dropping the chain left to right on the locker.
Was even more shocked at the 600euro or so pricetag for the bleeding thing!

Now planning to custom built a mushroom thing under the hole to spread the chain around. got all the bits down to a piece of 160mm dia etalon and hopefully will fix and test it next w/e

Since a great part of this whole thread is on locker fitting of chain, anyone care to point to any other option we could think of?

cheers

V.

 

[sarabande]

would it help a boat with a galv chain stacking problem to have a stainless cone or sides in the anchor locker ? That might reduce the natural angle of repose, at least initially.

 

[Magnum]

would it help a boat with a galv chain stacking problem to have a stainless cone or sides in the anchor locker ? That might reduce the natural angle of repose, at least initially.

A very good idea.

 

[WhiskeyTownRacer]

would it help a boat with a galv chain stacking problem to have a stainless cone or sides in the anchor locker ? That might reduce the natural angle of repose, at least initially.

Something like this perhaps? http://www.force4.co.uk/force-4-chain-boy.html?sqr=chain&#.WA0rPiRS1YA

No idea if it works as advertised and seems rather pricey for what it is, but no doubt substantially lower cost than SS chain. Of course it could also be useless, in which case the price is even more ridiculous.

 

[petem]

Surely Mk1 wife/foot is the perfect tool for the job? Perhaps suggest some steel toe cap boots if she complains?

 

[Neeves]

There is no 'time' to define when crevice corrosion may occur. Simply too many variables, warmer temperatures will increase potential, increased use will increase potential, damp locker will increase potential etc.

Part of the issue is that the locker is too small for the volume of the chain and also that it might be a design that does not allow the chain to flow into the volume of locker available.

Another part of the issue is that Magnum is going up in link size and in length and whatever volume of chain he has now will be but a shadow of the new chain.

Sorry to say this, again - but going down in size and buying a higher tensile product, so same strength, but much smaller volume will reduce weight (not an issue you say - try knocking a tower of 8mm chain over rather than 10mm or 12mm and you will notice a difference - or your wife will). If you go down in size but up in tensile strength you can reduce the volume of chain and still increase length. You then have a smaller volume of chain, its the same strength, its lighter so easier to knock the tower over and because it has a smaller volume it will only need de-towering about half the frequency of the larger chain.

As suggested you could have 4m of stainless on the bow, whatever distance between windlass and anchor.

The downside is that you will abandon catenary.

Most, off the shelf, gal chain is G30, Maggi and Peerless sell a metric G40 and G70. If you go down in size (from 10mm to 8mm), from G30, then G70 offers a similar strength to G30. 316 Stainless is a G30 strength, duplex stainless is a G60 strength. The numbers refer to the tensile strength of the steel, 300 MPa, 700 MPa etc. Most chain sold in the UK is now a min spec of G30 but tend to be near G40 quality and virtually all of it comes from China. Jimmy Green sell Maggi chain. Gal chain failure does not feature. If you go up in size, as you are/were doing then you need a new gypsy, if you go down is size, same issue.

G70 chain costs more than G30 but because you come down in size the differences are less than you might think. The same might be true of duplex stainless - because you might be able to come down in size the cost differences will not be so great.

There are other implications in going down in size than loss of caterary. You need to have an enlarged end link to allow you to fit a shackle that fits both chain and anchor (or in your case gal chain and stainless chain (if you go that route).

Much chain is sold in 'buckets' check what weight or length of whatever chain you choose fits in a standard bucket and compare with the next size up or down - it gives a very good indication of differences in volume and its more than you think (or at least I was quite surprised).

There does not seem any answer to chain towering, devices are discussed but there is no solution that is universally accepted (in fact I have never heard of anyone having any success other than) physically knocking the tower over. Broom and broom handles are popular - feet only work if you have long legs. Because our chain locker floor is completely flat we can push each 30m of chain into a corner - most people are not so lucky.

Jonathan