Best Alloy for 50 years life span in sea water anchor chain

[DungBeetle]

Best Alloy for 50 years life span in sea water anchor chain


hi guys.


i'm building my next catamaran right now and want an anchor chain.


anchor chain is commonly normal steel galvinised. you can imagine how long they last before they have to be replaced. not long at all, and they look rusty, stain everything red etc etc real quick.


common 316 stainless is useless. it ain't stainless. it doesn't last. it's CHEAP. and sometimes lasts LESS TIME than normal steel. we're talking MONTHS before it rots away utterly. All sailors know this, and so almost no sailors buy stainless chain.


so you have to constantly replace your anchor chain every three years.


this strikes me as a hit and miss, cave man sort of approach.

i'd rather do it once, and then never have to worry when you goto sleep at night about how old the anchor chain is when a storm approaches










MODERN alloys.
(did you notice the word modern was all in caps?)

316 (invented 100 years ago) starts Stress Corrosion Cracking at -5 degrees C

alloys with 6% molly start around 50 degrees C.



in other words, for the want of 3 cents worth of moly, no sailors buy stainless.


(and this is about the stupidest thing i've ever heard)







Remember;
Stress Corrosion Cracking is what it's all about.
ie Stress and Strain on the chain make it FAR more succeptible to chlorine, which dissolves the propagating edge of stress cracks inside microscopic cracks. The rest of the fitting looks fine but it breaks in half.

So a hot chain in the tropical sun.




Critical Crevice Corrosion Temperature (Degrees Celcius)

HASTELLOY® C-22® alloy 102
HASTELLOY® C-276 alloy 80

Alloy 2507, UNS S32750, 1.4410 60 PREN 43

HASTELLOY® C-4 alloy 50
HAYNES® 625 alloy 50
HASTELLOY® G-30® alloy 40
254 SMO (6% moly) 1.4547 ASTM 31254 40 PREN 43
Ferrinox 255, Aminox 255 45 PREN 40
FERRALIUM 255 35
Alloy 904L 20
Type 317LM Stainless 15
Type 317L Stainless 10
Alloy 825 -5
20Cb-3 alloy -5
Type 316 Stainless -5




Zeron 100 is suspect due to the absolute minimum 3% moly

http://www.ramaterials.co.uk/content/technical_general.aspx

and
it's built to the absolute minimum PREN specs to meet international standards; thus, same old problem of being as cheap as they can get away with.





Although Aminox255, Ferrinox 255, Ferralium have a good PREN, they are NOT acceptable as they dissolve in sea water 600 times faster than the higher grade alloys.

I am looking for a LIFE TIME chain. A BUY ONCE proposition.


I suggest 2507 has the MINIMUM properties required. Perhaps Zeron instead?


(Critical Pitting Temperature is not really of interest, and the absolute minumum PREN of 40 i suspect is pushing it, considering the chain has to still give sound sleeps at night 40 years down the track after being used every day.)

remember;
you guys know FAR more than me. i've read lots of the topics here and elsewhere, but DON'T KNOW for SURE what alloy is good for when i get my chain custom made. i don't want to specify some thing that engineers (you guys) will say; !you used 274! you forgot the tensile youngs modulus of pitting chafe! you can't use THAT for a chain. the obvious choice was 273! etc etc.








The question then;

there are FAR too many alloys out there and i don't know any real world stuff about any of them. (IT boy). are they in the ballpark? or are they so expensive as to be laughable?


So;
i'm hoping that some people here will know more than me about alloys, and be able to recomend the BEST alloy suitable for a LIFE TIME anchor chain.

It's all about sleeping soundly at night 20 years from now Vs cost Vs performance in sea water under strain for 40 years etc




Thank you for your time fellas,
hoping to hear suggestions from anybody.


mal.











(
Just for general interest;
and not part of this discussion;

sailors are losing their masts due to crap 316 rigging fittings suffering from Crevice Corrosion Cracking.
i'm having all my rigging fittings sourced from china, england, and india in 2507.

if you read all the stories in this thread,

http://www.cruisersforum.com/forums/f116/broken-rigging-photos-and-stories-please-60999.html

you'll see that 316 fails with monotonous regularity due to Stress Corrosion Cracking.




sour mud kills 316 anchor chains in 3 weeks

http://www.cruisersforum.com/forums/f2/stainless-chain-warning-2018.html

sour mud kills 316 in 1 week

http://www.cruisersforum.com/forums/f118/stainless-anchors-and-chain-4300.html#post35625

all for the want of 3 cents of moly
)

 

[MikeHalloran]

I used to work in a marine exhaust shop.
Some of our competitors used 304. We got lots of business from their former customers.
We offered a 1 year warranty on products made of 316/L.
We offered a 5 year warranty on products made of 254 SMO or AL6XN or one other similar alloy.
We did not offer a longer warranty on anything.


You are asking a lot.

Anything with much iron in it is probably not going to work for you.
Nickel alloys might offer some hope, but they get very expensive very quickly and can be difficult to fabricate.
I'm guessing there are a few copper alloys that might work for you, but copper has a very high rate of evaporation after midnight.
Titanium and FRP have good resistance to seawater, but not to the abrasion inherent in a chain.
Modern polymer ropes can do well, except for abrasion on rocky bottoms, so you still need a bit of chain near the anchor itself.



How about contracting with someone to come to your boat and replace a galvanized steel chain on a regular basis, say once a year? Even including labor, travel and transportation costs, even for 50 years, that could be cheaper than some of the alternatives already proposed.







Mike Halloran
Pembroke Pines, FL, USA

 

[zeusfaber]

One of your biggest constraints is going to be the list of materials that respectable cable makers are prepared to work with.

With the volume of business you're going to offer, it's hard to see their incentive for experimenting with anything unfamiliar.

A.

 

[EdStainless]

There is no 'corrosion rate' for high alloy materials. All of the serious corrosion is localized pitting/crevice.
While Crevice corrosion on 316 will start at low temps (ambient) in seawater it will not suffer CSCC until higher temp (40C).

The biggest problem for the chain is not service, it is how it washed prior to storage.

A 6%Mo superaustenitic (AL-6XN, 1925hMo) or a superduplex (Z100, 2507, 255) should be drastic overkill, and will be 10 times the price of 316 if it was in standard production.
If you can manage to pressure wash the chain when you raise anchor and store it then an alloy like 2205 should last forever. It has lasted decades on pier jackets and legs of oil rigs.

The duplex alloys have the advantage of superior CSCC resistance (even over the 6%MoSA alloys) and a high strength.
If you can't wash the chain and you want to ignore it then you would need a Ni-Cr-Mo alloy (59, 622, 686) and the price goes back through the roof.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[DungBeetle]

Hi Mike,

thanks for helping.
real world stuff is always good.



STEELS

Al-6XN is a great suggestion. at this point in time i say it leads the pack of the steels.


"Anything with much iron in it is probably not going to work for you."

i think you're right.

to make it 50 years, the life span has to come from the total metal, not just a thin surface protection film.

the chain is moving, grinding on itself, rocks and coral and constantly breaking the thin chromium oxide surface passivation protection layer, and then it gets dropped in sour mud the next time, and the microscopic cracks fill with sour that stays there.

i think you're right. the steels are out.







COPPERS
from my brief reading,

Silicon Bronze is out because it's tensile strength ranges randomly from 103 MPa to 483 MPa, and has a corrosion rate of 0.025 mm per year, which times 50 years is loss of over 1mm off an 8mm chain. too much metal lost.

Copper Nickle 70/30 has no corrosion cracking and long term corrosion rates of 0.001 mm per year, so i guess this is currently a candidate








NICKEL

what about nickle alloys then?

my brief reading suggests some of them get NO stress corrosion cracks at all

according to page 22 of "Nickle stainless steels for marine environments"
625 has the least drop in strength percent after 100 million cycles in sea water

if the chain is stressed to 25% of it's breaking strength every ten seconds (waves) for 50 years;
86400 seconds per day div 10 for wave periods gives 8640 stress cycles per day
times 365 = 3 153 600 per year
31 million per decade, so 100 million cycles gives 30 years


the maximum stress at which failure will not occur is the highest for 625 in terms of percent of it's original unstressed strength.


so i can stress to 25% of ultimate tensile strength continuously for a good solid realistic 50 years.






EXOTICS

Zirconium Alloys ??

Titanium Alloys ??

i say definitely viable. i was originally going to get this chain custom made from 2507, but i recently got heaps of quotes on hundreds of 2507 bolts, and titanium alloys came in at HALF the cost of the 2507 stainless.

(i was shocked at the cost of 2507)

"Titanium is not an 'exotic' metal, it is relatively inexpensive and widely available."

so titanium is definitely a contender,

"The outstanding corrosion resistance of titanium even in heavily polluted sea water, offshore produced fluids and all but a few non produced fluids is due to the metal's stable, tenacious and permanent oxide film"

what happens when this wears off? ie chain links grinding on each other?

Stress Corrosion Cracking

http://cartech.ides.com/datasheet.aspx?i=101&E=269

http://www.sciencedirect.com/science/article/pii/0029801870900041

ROPE

"Modern polymer ropes can do well, except for abrasion on rocky bottoms, so you still need a bit of chain near the anchor itself."

most live aboard cruisers in the pacific use ALL chain rode. common stories of peeps anchoring, going ashore for customs, and 1 hour later their yacht is adrift or on a reef. coral heads cut good rope in an hour.

(guys from cold countries use rope in the rode though.)

so the anchor rode will be all chain.






COST

"How about contracting with someone to come to your boat and replace a galvanized steel chain on a regular basis, say once a year?"

you're not in the groove here, not onside, not achieving resonance,



see,

YOU'RE saying;
isn't it stupid that i'm the only person on the planet who wants a chain suitable for use in sea water.


whereas I'M saying;
isn't it stupid that i'm the only person on the planet who wants a chain suitable for use in sea water.


the two statements are entirely opposite each other in meaning.










8mm 316 stainless chain is $30 meter @ 1.5 Kg

which is exactly the same price per kilo as C-276 (just got a quote today), so all i pay extra for is the fabrication cost (to a small local chain making firm)



a brand new 55 foot catamaran can cost you a million dollars.

so mow much extra would YOU pay if it was YOUR catamaran? the single line to safety when you are asleep in a storm?


(
i've not yet got the fabrication cost, but i presume it will be under the "replace your normal steel chain 50 times instead" cost
)



thanks mike.
onya,

mal

 

[EdStainless]

625 is that corrosion resistant is seawater.
If you plan on allowing for dried salt deposits, biofouling, mud and muck, and so on then you are back to Ni-Cr-Mo (622, 686, 59).

There are some high strength Cu alloys but they will not take H2S exposure.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[cloa]

How about some high alloy cast irons?

 

[DungBeetle]

Hi Ed,

great stuff!
and thanks.




about the cost;
i presume you read the above about my 2507 bolts being TWICE the cost of the titanium ones?


so firstly,
it's hard to believe that anything can cost more than 2507.


and secondly;
i have in my posession the most valuable object known in the world.

(my arse. it's doubtfull that there exists a more valuable or important item anywhere on the planet)



sure the catamaran may cost a million dollars, but what about the IMPORTANT item?

and the life of all of this stuff is riding on a single chain. i say that normal chain is NOT sensible, not when compared to the cost of all the other stuff.


how much is an alloy that does the job PROPERLY worth? nowhere near as much as all the stuff that depends on it. not even in the same ball park.

so cost is relative.









"2507 is overkill"

(2507 was my first choice for the chain, but i've been reading heaps and heaps of technical documents and got my head full of all the gunk about Stress Crevice Corrosion Cracking in HCl and FeSo4 solutions.

[
my current (undoubtedly wrong) understanding is that i have to get an alloy that has no Stress Corrosion Cracking while lying in the hot sun
(you know all those studies about getting a bar of alloy, stressing it to 25% breaking 100 million times while spraying sea water over it. some of the cheap stainless fails astoundingly quickly, hours, all due to a tiny bit of salt water.)
]

and;
according to all the steel makers DATA, 316 is ACE!
but i've seen and read so many stories about guys loosing their masts and rigging due to a $10 toggle or fitting failing, that i'm having all mine done in Aminox 255 (same as Ferrinox 255) (because that's the only stuff i've been able to find fittings in)




so if alloy manufacturers DATA pages on the web say 316 is ACE, groovy etc, then this is why i'm after the
.
.the what?
.excess capacity?
.overkill?
undoubted performance,
a better alloy than needed due to heavy scepticism. (i can't believe anybody but a moron would use 316 for rigging; loosing your mast in the middle of a storm is SERIOUS, life threatening, and it happens everyday)





"While Crevice corrosion on 316 will start at low temps (ambient) in seawater it will not suffer CSCC until higher temp (40C)."

See? even you say 316 is ace, and yet the links in the very first post on this thread show 316 FAILS with Stress Corrosion Cracks in COLD water almost immediately. not months, but WEEKS until SCC breaks it in half. this is the normal behaviour of 316.

Everything i've ever read said;
The Pitting Corrosion temperature of 316 is 17 Degrees Celcius in sea water. So it starts to dissolve at 17 degrees.

But when stress and strain add some of the energy needed, it starts to dissolve at -5 degrees Celcius in sea water. (Stress Corrosion Cracking)

Many studies found the same thing, -5 degree C, and this agrees perfectly with the reality of broken 316 chain and rigging in low temps under very little stress.



so i went looking for what you said and DID find

http://www.sandmeyersteel.com/316-316L.html

stress corrosion cracking (SCC) @ 49°C

but i'm at a loss to explain what they're on about or where they get their data from, as again, every single study i've read all agree on -5°C

and on a different page on the same web site they say
-5°C
316 Critical Crevice Corrosion Temperature as determined by ASTM G48 method F; 6% FeCl 1%HCl; a approximation of years of salt water service

http://www.sandmeyersteel.com

http://www.haynesintl.com/HASTELLOYC2000Alloy/HASTELLOYC2000AlloyCD.htm

says Critical Crevice Temperature of 25 degrees
and yet they also say

-5°C
but; for this solution only-
316 Critical Crevice Corrosion Temperature as determined by immersion in oxidising 4%NaCl, .1% FeSo4, .01M HCl
an approximation of years of salt water service








hmmmmmm.

i suspect that i'm confusing Stress Corrosion Cracking Temperature and Critical Crevice Corrosion Temperature etc etc

and i freely admit to being confused about engineering terms.

i just assumed Stress Corrosion Cracking Temperature and Critical Crevice Corrosion Temperature were the heart of the matter.

i do KNOW that i am NOT competent enough to be able to comment on alloy properties.

i only know enough to be a danger to myself and others.










so Ed,

i think i'll let you decide for me.





considering the life span requirement and conditions then,
what alloy would you go for?
still 2507?

what's your personal number one?

what alloy would you use to guard your life while you sleep 20 years from now ?

 

[DungBeetle]

The Contenders List



.2% Yield Strength MPa Tensile Strength

C-2000 379
C-22 370
C-276 355
Inconel 686
Ultimet


Al-6XN 310 690
2507 550 800


Titanium 880 950
(Ti-6Al-4V)


316 500








#1 - The Top Spot (so far)

2507 (S32750)

i'm sceptical about the life span in sour mud, but Ed is a supporter
i'm sceptical about the cheap 4% moly level. why not 6%???
good yield strength

2/ Titanium





Nickel Alloys
only drawback is the low yield strength

1/ C-2000 the top spot in the nickels Strong Contender to take to title.
Critical CCT 110°C Crevice Corrosion basically zero

2/ C-22
Critical CCT 102°C, Crevice Corrosion basically zero

3/ C-276 15Cr 55Ni 15Mo, Crevice Corrosion basically zero

4/ Inconel 686 a leading contender Crevice Corrosion basically zero
doesn't get stress cracks



Titanium?? i say it's a strong contender

(due to it's yield strength, and the fact that it is available in chain off the shelf. i don't have to get it custom made.)


whats wrong with titanium chain anybody??

 

[cloa]

Titanium is easily abraded. A few surface treatments to get around that- will they last 50 years.

 

[EdStainless]

Ti has poor fatigue properties and can be highly notch sensitive.

686, C-22, 622, 59 are all virtually identical Cr-Mo-Ni alloys and would work even in the highly cold worked condition.

2507 (and other super duplex grades) have a different microstructure and use alloying elements differently. These alloys have enough strength to be useful in the annealed condition. All of the other grades that you have mentioned would need to be used in a cold worked condition to achieve higher strengths.

I find it a poor use of expensive alloy when washing off 2205 would be more than suitable.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[unclesyd]

In that you have danced around very good advice for your application by using SCC I am going to disagree with you about the failure of marine hardware. I've seen a lot failures of hardware and fittings and I have to say that fully 90% have been due to overload not SCC. Every Mast failure I've seen has been having too much sail at the wrong time, just looked at a 36' who's mast broke in the middle. It bent and don't crack.
I agree that he numbers you are looking at are guide lines, nothing in solid stone. There has been a 87' shrimp boat with a hull made from Inconel 600 in service in the Caribbean for over 40 years with no problems. On our little 47' wooden fishing boat we have a 316 SS muffler exposed, since 1960, to the weather, the chain plates (8) are 316 SS with SS bolting, since 1965. We now have 1 steel mast instead of two wooden ones and use 5/8" 316 bar as stays, the turnbuckles are HDG, wrapped. Until recently our fishing lines were 316 SS 7x7 construction. These would last for years. We used both bare and nylon covered wire rope.
I Don't understand the reference to a million dollar boat floating free with all the anchor watch equipment around. By the way we have 150 fathoms of 1" twisted Nylon for the anchor rode, with another 100 fathoms stored. The lead chain 30' is HDG and last for 15+ years. I went down today and looked at two motor sailers and both had HDG anchor chain. Both were using the special rounded HDG windless chain.

How much chain are you considering?
A material not mention above is Nitronic 50. I've seen some relative short sections of chain made from this material.

 

[JamesCKelly]

I worked for a supplier of specialty heat and corrosion resistant alloys. Metallurgist, wrote all the technical data sheets.
Corrosion data, CPT, tensile, yield are all very interesting and surely must be considered.

But there is one more very important material property.

And that is AVAILABILITY

What high alloy materials are actually available as chain?

Things like AL-6XN, 254 SMO, 625 and Inconel 686 should give many years of service. But which one can you actually buy?

Speaking just as a metallurgist, I would avoid the various copper alloys, as they do not suit near shore, where sewage (sulphur compounds) is discharged. Of the duplex alloys 2205 is not suitable for long term seawater service. Specifically not in North Sea oil rigs. If you like duplex, the choices would be 2507, Zeron 100 or Ferralium 255. I might note that it is harder to make a fabrication mistake with AL-6XN or 625 than it is with any duplex.

But do find out what materials are actually available as chain. That will cut down your list to a small number of alloys to consider.