Stainless chain

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ip485

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Is stainless chain worth the extra cost?

I have 100 metres and stainless is £3.5K more, a significant sum.

I appreciate the working loads are significantly higher.

Anchoring a lot on coral sand and I read cruisers find the eroding action of the sand wears through chain very quickly - well before rust takes hold. Is this equally as true of stainless, and do you end up just replacing the chain as quickly when used regularly?

Perhaps it lasts a lot longer if not anchoring on such a regular basis?

I seem to recall reading some while back that stainless doesnt deal with shock loads very well either when used for chain?
 
Wear rate is a function of hardness, which is itself related directly to strength. Grade 50 Cromox would therefore be expected to wear less than Grade 30 316. Galvanised steel chain is difficult to predict as the zinc is softer but the iron-zinc alloy is harder, maybe harder than Grade 30 steel (?). I don't know but I suspect it is.
I cannot imagine shock loading being a big issue, especially with a snubber.
 
Vyv summaries well :)

Shock loading is, I suggest, a red herring - you should be using a snubber, as Vyv says, - there will be no shock loading.

The alloys of galvanising, those Fe/Zn alloys, are harder, thus more abrasion resistant than the underlying steel (and harder than Grade 50 Cromox (stainless). The outer layer of zinc is soft - and will abrade relatively quickly, the alloy layers underneath will last longer. The abrasion resistance is also a function of the amount of hard material, in the case of Cromox the diameter of the wire from which the chain is made, say 8mm - but the galvanised layer its usually only about 100 microns (and varies). In a very abrasive environment the galvanising will not last long, in the grand scheme of things there is not much galvanising :( compared to the amount of stainless.

Most anchor chain is G30 or G40, it is protected from both corrosion and abrasion by the chemical properties of the Zn and the hardness of the alloys - but once the gal is lost the underlying steel will wear even more quickly than did the gal coating, because it is softer. Consequently when your 'normal' G30/40 chain starts to rust it needs to be galvanised quickly, relatively speaking, as you will now suffer accelerated wear, both corrosion and abrasion. The Cromox G50 chain will last longer - because it is harder - but it cannot be redeemed - once it has gone, its gone.

I'm obviously going to mention it - galvanised high tensile chain will last longer than G30/40 because it is harder (and the gal will last longer if Armorgalv coated because the galvanised alloys are harder) - but once the alloys have gone you then, again have that double whammy of corrosion and abrasion, even if the abrasion is slightly less (than G30/40).

I have some data on the wear rates of steels of different hardness under abrasive conditions but they would not support what looks to be a 3 times cost for a rode (you are not going to get three times the life).

A better option might be to accept the higher wear of the conventional rode and ensure you are in a position to regalvanise when necessary.

I'm not sure that regularly used G30/40 chain will show much sign of rust - every time the chain is deployed it will be rusting, corroding, but that tell tail brown coating is constantly being abraided (it is really soft) and every time you retrieve you will have lovely shiny chain. Iff you move a few miles it might not have much time to rust in the locker - before you deploy again, and grind off any surface rusting. Instead of looking for 'rust' you should be measuring the wire thickness, the thickness of the chain (and doing this for stainless as well - as the loss of thickness will be insidious in cora)l. As you would normally end for end - I'd suggest cutting some new, fresh, links off before you use the chain as you then have a standard against which you can compare the rode itself.

Stainless offers other advantages, it is said to tower less easily and it is less prone to chemical attack in muddy anchorages (though if you are looking at coral - not much mud) and it is also very pretty.

Jonathan
 
316 work hardens a lot but wears easily in abrasive conditions. If you are doing a lot of anchoring in sandy conditions i would save the 3.5 k and go for galvanised chain. In either case its a good idea to "end to end" the chain ( i.e. swap the anchor end round to the boat end) every year or so to even up wear. Another tip is to get the chain 15m longer and cut off a few metres from the worn end when you end to end. This will increase chain life.
 
I know of two instances where stainless steel chain lasted less than a year. Both were in the tropics and the chain was in more or less constant use. The chain did not break but the skippers decided to repurpose the chain when large deep black pits started appearing on the chain.

In both cases they went back to galvanized chain.
 
TQA said:
I know of two instances where stainless steel chain lasted less than a year. Both were in the tropics and the chain was in more or less constant use. The chain did not break but the skippers decided to repurpose the chain when large deep black pits started appearing on the chain.

In both cases they went back to galvanized chain.
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Yes, I have a photo (printed in YM) of some 316 chain (supposedly) with very deep pits in the wire, not the weld. That one was taken in the Caribbean but I don't know its source. Cromox should be better in almost every respect although genuine 316 should be satisfactory for most purposes.
 
vyv_cox said:
Yes, I have a photo (printed in YM) of some 316 chain (supposedly) with very deep pits in the wire, not the weld. That one was taken in the Caribbean but I don't know its source. Cromox should be better in almost every respect although genuine 316 should be satisfactory for most purposes.
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Cromox being stronger would give the opportunity to down size the chain, maintaining strength of the appropriate G30 for the size of vessel. Cromox is of a similar strength to Peerless galvanised G70. This will obviously save weight in the bow but also means you would only need to buy 8mm, Cromox, instead of 10mm gal G30 chain (saving some money) or 10mm 316.

The spread sheets of chain vs vessel size seem fairly robust - reports of G30 chain failing have not been available for years - G30 is strong enough if correctly sized and seems to have the 'right' level of safety factor. Most complaints about chain recently, last 10 years (?) have been about galvanising quality - not the chain itself.

I'm not sure of the hardness of 316 but, and I hate guessing, suspect its near that of conventional G30 (which is not very abrasion resistant).

There is a lot of stainless chain coming from China and whereas some I am sure is of an excellent quality some is absolute rubbish. If it looks too good to be true, have some tested - otherwise buy from a reputable manufacturer but given the size of the investment it would not be unreasonable to ask for a QC certificate anyway. I think CMP offer stainless chain and Maggi were threatening to add to their portfolio. You will also need decent connectors, shackles - they will not be cheap either. Finally you need to ensure the anchor shank is, also, duplex steel - or you might expect it to bend like a kirby grip. Many stainless anchors are made from 316 - but they still need a strong shank (which will not be met by the strength of 316 unless the shank is very beefy).

Jonathan
 
I made these for a client with a very expensive sailboat and he expressly specified a4 316 stainless but I don’t know how he intends on using them. I’m guessing they’re not going to be very useful as anchor chain.

PS. sorry I just could not help myself. :D


CzONPyg.jpg
 
Jonathan - the strength of 316 stainless is very similar to that of mild steel. So the hardness would also be similar to that of a genuine grade 30 steel. As we know, many Chinese chains contain some alloying elements and would thus be a little harder.
 
vyv_cox said:
Jonathan - the strength of 316 stainless is very similar to that of mild steel. So the hardness would also be similar to that of a genuine grade 30 steel. As we know, many Chinese chains contain some alloying elements and would thus be a little harder.
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Then I would expect 316 stainless to last a bit longer than G30, because it would wear similarly from abrasion but would not suffer wear through corrosion. I find it difficult to believe that corrosion wear would be so significant to justify (by itself) the extra cost of stainless.

People buying, 316, stainless chain appear to be very few and far between and I cannot recall seeing any reliable description of performance - other than those who are disappointed (and they might not have bought from a reputable source).


I tested some stainless chain (from China), ostensibly 316. it was absolutely beautiful - if you like shiny metal (and I can be a fan). It failed, as you suggest at a similar strength to G30, but its yield was much lower, (around 50% of UTS) and because lower the percentage yield was higher (than G30).


Interestingly the charter operators that I can think of that operate in coral waters and whose yachts would normally only, or very predominately, anchor in coral sands use conventional galvanised chain, and in Australia that would be a G30 quality. I might have thought that if stainless offered an advantage it would be acknowledged - somewhere. I can see technical advantages of duplex (ie Cromox) - specifically weight saving, no fears of losing 'gal', less risk of towering (it is pretty- and you cannot price that) - but I don't recall anyone buying Cromox (nor 316) because they think it cheaper (in the long term).

One good thing about Cromox - you can buy a rode of compatible components, matching for size, fit and strength - much more difficult to achieve this with a G70 from Peerless or Maggi - where you need scratch around yourself to find components that 'fit'.

Jonathan
 
I am now intrigued :)

I have some 8mm short link 316 chain, see previous post, and a variety of samples of galvanised 8mm or 5/16th" chain, G30, 40 and Peerless G70 (some American 100 micron Armorgalv coated G80 and Australian coated G100). I'll run a long term abrasion (and corrosion) test on the seabed here. Ideally I could do with including Cromox - but that might not be feasible (I'm not buying it!) - but I'll try to beg some.

I don't have coral sand but our sand (most of the southern part of Australia's east coast) is silica (quartz) based. Thinking about it I'm not sure why coral sand should be more abrasive than silica sand, in fact it should be significantly less abrasive (and very, very few people here use stainless chain - think bigger MoBos). I can see coral being more abrasive than sand - but you should not be anchoring in 'attached' coral anyway (destroys the coral and makes retrieval a bit of a lottery).

Jonathan
 
The low yield strength of 316 is certainly a negative factor. It is conceivable that a good heave or shock load could deform the chain such that it no longer fitted the gypsy but would otherwise be perfectly serviceable.
 
Neeves said:
He is an Indian snake charmer and thought they would match his Kobra anchor (for which he is awaiting delivery) :) ?

Jonathan
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That’s one of the best I have heard so far ! +1 :encouragement:
On a serious note my humble opinion is that they both suffer in aggressive environments and we only have anecdotal evidence to go by. In the end it comes down to a question of how much money you want to spend on a chain as you will either be cutting a few meters of stainless, or mild steel for different reasons same result.
I have been known to be wrong off course. ( as my wife likes to point out )
 
Neeves said:
Stainless offers other advantages, it is said to tower less easily and it is less prone to chemical attack in muddy anchorages (though if you are looking at coral - not much mud) and it is also very pretty.
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These are the key points imho, given that in most cases you will not feel any other differences between 316 ss and galv steel of any sensible grade. S/s polished chain flows like cream into the anchor locker. It doesn't tower/pyramid anywhere near as much as chalky galv chain. Thus you can fit much more length into your locker, or have a smaller locker for same length, either of which might be what you want. And it looks prettier, fwiw
 
I will be testing duplex stainless, specifically Cromox, in a seabed abrasion test in comparison with galvanised chain of various qualities. The results should indicate whether the harder steel of Cromox results in an appreciable reduction in abrasion and take some of the guesswork out of making a decision on purchase. JFMs comments remain valid - stainless does not tower as galvanised chain does and carries less, or no, mud when retrieved and given that towering is a repetitive gripe regarding galvanised chain (and has few answers) on these forum it is a very real issue.

The opportunity to reduce link size from 10mm, say, to 8mm - in the same way you can reduce chain size if you opt for G70 chain also reduces the issues of towering further and means you don't need to consider buying expensive 10mm Cromox but slightly cheaper (but still expensive) 8mm Cromox.

As a user of reduced size chain I can confirm there have been no issues with downsizing and any fears expressed are specific to that manufacturer's chain and not downsizing in general. I ran another series of abrasion tests to confirm this - and take the guesswork out of criticism of small link chain, I only wish we had downsized earlier. But - you do need to use a snubber.

On the testing - I don't know when I will receive the sample, it might be delayed until March and then takes at least a month for testing - wear is depressingly quick on some galvanised chain - no wonder some galvanising does not last.

Finally, to those that read threads with an 'anchoring' focus -


Merry Christmas and best wishes for the New Year.


Jonathan
 
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