Anchor chain

Galvanised chain has been in use for what? centuries? Now we want to repair something that isnt broke? By the way, my chain has been aboard for 40 years, I've been anchored quite a lot in the last 14 years whilst living aboard, my chain is still good and it's never been re-galvanised, so why would I want to go for stainless, when I can buy european manufactured, calibrated 1/2" chain, for my new windlass? I'lkl stick with what I know, thanks.
 
I dont think anyone is asking you to change to Stainless, it's your choice.. I prefer to use SS at the same price or cheaper than galv, it has the same performance and safety limits as standard galv, is cleaner to use and stow.
No woriies, stick to what you want...
We tryed to have 60 mtrs of HT Galv regalved here, not a chance.. and it is getting harder all over the world to do such, and, more expensive.
I'll personally stick with the better option.
 
>Anchors come up and down, sometimes many times a day, sometimes once a week occasionally once every 2 weeks, very occasionally a bit longer. Anything down for 7 months is 'moored' not 'anchored' so I'm not surprised they had an issue.

The very great majority of yachts anchor as you say but long term cruising boats often pitch up somewhere, fall in love with the place, and stay for a long time (the record we have seen is over three years), six months at anchor every year is not unusual in hurricane season (visit Curacao to see what I mean - 100 plus boats at anchor). Such boats shouldn't use SS chain, which I think you agree with.
 
I suspect that you are misinterpreting the information that you have provided. The corrosion that Azom discusses is clearly stated to be 'surface' associated with crevices and surface roughness. We have all seen evidence of crevice corrosion, in stains around fasteners and under fittings. The most common evidence of surface roughness having a similar effect is on rigging wires, where the drawing operation can cause surface flow and engender minor crevice corrosion in seawater.

However, none of these is likely to be catastrophic in normal circumstances. Minor surface roughness on chain is likely to cause a little staining but this is a long way from causing the chain to fracture. In fact, vitually all metals suffer from crevice corrosion, a good example being domestic radiators that fail at the acute joint between the two sides.

As has been pointed out, the quality of chain manufacture varies enormously and it is the poorer examples of these that suffer the most failures.

The corrosion protection of stainless steel prop shafts is provided by its coating of chromium oxide, not by any anode that may be fitted.
 
Hmmm, very interesting comments, & all things considered...I'm starting to swing back to Galvanised chain now.
As suggested-I wouldn't go to the expense of changing my chain just to get SS but there was only 15 metres of galvanised 3/8" chain came with my boat, which I suppose I can use on a kedge-anchor now, so I can start off with a clean slate for the main bower anchor.
Thanks to all for the comments, links & advice.
Jock
 
Stainless the same price as galvanised!!

Either one is being conned about the quality of the stainless or grossly overcharged for the galvanised.

I've had a fair bit to do with the chain-manufacturers of Cradley Heath and know that's not a likely scenario.

I'd agree that IF stainless were as strong as galvanised steel and it were the same price I'd definitely plump for it.

Heigh Ho for those soaring pigs!!!
 
Stainless steels

are a very large group of similar metals - generally 304 is used above the waterline and 316 below.
None of the stainless alloys achieve the strengths of some carbon steel alloys or some of the more exotic (and corrosion resistant) bronzes.
I doubt the failure quoted was primarily due to crevice corrosion - more likely fatigue, to which 316 is notoriously prone - hence some express a preference for 304, even though its corrosion resistance is lower.

Here's a list of some of the more commonly available varieties

Stainless 15-5ph
Uns S15500 (Ams 5659)
This grade is a Cr-Ni-Cu precipitation hardenable Steel, which has good strength and corrosion resistance. The material grade can be used in the Solution Treated condition or heat-treated for various applications such as Aerospace Components, fabricated parts in high-pressure corrosive environments including valves, shafts, Landing Gear Equipment, fasteners, fittings and gears.

Stainless PH 13-8 MO

Uns S13800 (Ams 5629 / Ams 5864)
This grade is a Cr-Ni-Al-Mo precipitation hardenable Steel, which is capable of high strength and hardness along with good levels of resistance to both corrosion and cracking. Applications are Aerospace Components, Valves, Petrochemical and Landing Gear Parts.

Stainless Steel 17-4ph
Uns S17400 (Ams 5604 / Ams 5622 / Ams 5643)
This grade is a Cr-Ni-Cu precipitation hardenable Steel, which combines high strength and hardness with exceptional resistance. It is corrosion resistant in some chemical, petroleum, paper, dairy and food processing industries (equivalent to 304L grade). Applications and industries are Offshore, Medical Equipment, Mechanical Components and Aerospace / Power Generation Turbine Blades.

Stainless Steel Grade 304
Uns S30400 (Ams 5511 / Ams 5647)
This grade is a Cr-Ni Austenitic Steel, which is the most versatile and most widely used Stainless. The balanced austenitic structure of Grade 304 enables it to be severely deep drawn without intermediate annealing, which has made this grade dominant in the manufacture of drawn stainless parts. This grade has many applications such as Food processing equipment, Heat Exchangers, springs and Threaded Fasteners.

Stainless Steel Grade 316
Uns S31600 (Ams 5507 / Ams 5653)
This grade is a Cr-Ni-Mo Austenitic Steel, which is the standard molybdenum-bearing grade, second in importance to 304 amongst the austenitic stainless steels. The grade has exceptional Welding and forming Characteristics. The austenitic structure also gives these grades excellent toughness, even down to cryogenic temperatures. The applications to this grade are similar to 304, such as Heat Exchangers & Threaded Fasteners.

Stainless Steel Grade 321
Uns S32100 (Ams 5510 / Ams 5557 / Ams 5570)
This grade is a Cr-Ni Austenitic Steel (Titanium stabilized), which are used because they are not sensitive to intergranular corrosion after heating within the carbide precipitation range of 425-850°C. Stainless 304L has lower hot strength than 321 and so is not the best choice if the requirement is resistance to an operating environment over about 500°C. Applications are Aircraft exhaust manifolds, Expansion Joints, Furnace Parts, Heating element tubing and Heat Exchangers.

Stainless Steel Grade 440c
Uns S44004 (Ams 5618 / Ams 5630 / Ams 5580)
This grade is Cr hardenable Steel, which is capable of attaining, after heat treatment, the highest strength, hardness and wear resistance of all the stainless alloys. With its High Carbon content, this grade is preferred for most Ball Bearing and Valve applications.

Stainless Steel Grade 403
Uns S40300 (Astm A276)
This grade is a Cr Steel hardenable by heat treatment, which has a lower strength due to the Carbon content and is a lower corrosion resistance grade. The Chromium levels are between 13-17%, which makes this material ideal for Turbine Applications, Missile Rocket components & Medical Instruments.

Stainless Steel Grade 410
Uns S41000 (Ams 5504 / Ams 5505)
This grade is a Cr steel hardenable by heat treatment, which will attain high mechanical properties after heat treatment. It has good impact strength, corrosion and scaling resistance up to 1200 F (649 C). Applications are steam and gas turbine blades and buckets, bushings, valve components, fasteners, screens and kitchen utensils.

Stainless Steel Grade 420
Uns S42000 (Ams 5506 / Ams 5621)
This grade is a Cr hardenable Steel, which is a higher Carbon version of Grade 410 with a minimum of 12 per cent Chromium, just sufficient to give corrosion resistance properties. Its best corrosion resistance is achieved when the metal is hardened and surface ground or polished. Common applications for this grade are Medical and Turbine instruments.

Stainless Steel Grade 422
Uns S42200 (Ams 5655)
This grade is Martensitic Cr Steel is a standard Martensitic, which is also known as plain chromium steel. Sometimes used in the annealed condition, 422 stainless steel bars achieve its best corrosion resistance when hardened then stress relieved. Applications are Gas Turbine, Steam Turbine, Oil and Gas compressor Parts.

Nitronic 50
Uns S20910 (XM-19 / Ams 5764 / Astm A182)
This grade is a registered trademark of Armco Steel.
This grade is a Cr-Ni-Mn-Mo Austenitic Steel which provides a combination of corrosion resistance and strength, not found in any other commercial material available in its price range. This austenitic stainless has corrosion resistance greater than that provided by Types 316 and 316L. Common applications are Marine Pump Shafts, Valve fittings & high strength Fasteners.

Nitronic 60
Uns S21800 (Ams 5848)
This grade is a registered trademark of Armco Steel.
This grade is a Cr-Ni-Mn Austenitic Steel which provides excellent high-temperature oxidation resistance and low-temperature impact resistance.
Applications are Valve Sterns, Fastening Systems and Pump contents.

A286
Uns S66286 (Ams 5726 / Ams 5731 / Ams 5732 / Ams 5737 / Astm A453)
This grade is an Iron based super alloy, which is known for its resistance to corrosion and retention of strength in elevated temperatures. The material is mainly used for machining Gas Turbine, Steam Turbine and Aerospace Parts.

Jethete M152
Uns S64152 (Ams 5718 / Ams 5719)
This grade is a high strength Alloy Steel has very good toughness and creep rupture strength. Excellent for use in highly stressed turbine blades as well as turbine discs, screws, shafts, bolts, pins and rings.

Maraging Steel 250
Uns K92890 (Ams 6501 / Ams 6512 / Ams 6520 / BS S162 / Mil-s-46850
This grade is a low carbon Maraging steel with excellent toughness and ductility. The alloy has good fabrication characteristics, which include a low rate of work hardening, good Machinability and weldability, and a very simple heat treatment process. The applications are Missile components, tooling and Jet Engine Shafts.

Maraging Steel 300
Uns K93120 (Ams 6512 / Ams 6521 / Mil-s-46850)
This grade is a high strength Iron, Nickel, Molybdenum and Cobalt alloy with good ductility and Machinability. The material is used for very high strength structural applications such as aircraft land gear components.

Custom 450
Uns S45000 (Ams 5763 / Ams 5773 / Ams 5859 / Ams 5863)
This grade is a registered trademark of Carpenter Technology Corporation.
This alloy is a Martensitic Age Hardenable Stainless, which has very good resistance to corrosion and moderate strength. The material is mainly supplied in the Annealed condition and requires no further Heat Treatment for most applications. The material is used in the Aerospace, Gas and Steam Turbine Industries for machined components and turbine blades.

Custom 455
Uns S45500 (Ams 5578 / Ams 5617 / Ams 5672 / Ams 5860)
This grade is a registered trademark of Carpenter Technology Corporation.
This alloy is a Martensitic Age Hardenable Stainless with good resistance to atmospheric environments. This alloy is extremely stable during heat-treating so it can be machined to close tolerance prior to aging. This grade is used in critical Aerospace and Defence applications. This can also be used in the Electrical and Turbine industries.

Custom 465
Uns S46500 (Ams 5936)
This grade is a registered trademark of Carpenter Technology Corporation.
This alloy is a Martensitic Age Hardenable Stainless with exceptional tensile strength and corrosion resistance. The strength of this grade is superior to that of Custom 455.
The applications are generally used in the Aerospace and Defence Industries.
 
Englander, I completely agree with you, if it's not broke why fix it. 40 years without re-galving your chain, you really need to use your boat more.

[ QUOTE ]
The very great majority of yachts anchor as you say but long term cruising boats often pitch up somewhere, fall in love with the place, and stay for a long time (the record we have seen is over three years), six months at anchor every year is not unusual in hurricane season (visit Curacao to see what I mean - 100 plus boats at anchor). Such boats shouldn't use SS chain, which I think you agree with.

[/ QUOTE ]
Absolutly agree. Like most things on cruisers you do have to make compromises and adjust things to suit your needs. Just like you don't have full main up in 50kts you also don't anchor for extended periods on SS gear.

[ QUOTE ]
Either one is being conned about the quality of the stainless or grossly overcharged for the galvanised.

[/ QUOTE ]
In some case many are being conned about the quality of a lot of SS gear these days. As vyv_cox mentioned above quality of manufacture has a massive input into how things will go over time. Some of the SS out of the east rusts after a month of use. Many would think that shows some SS is not as pure as it should be.

There seems to be a lot of cost pressure on general gear made of steel so I wouldn't be surprised to see many price increases this year. As for the price of stainless (and copper and oil and many other things) blame to suits sitting on the 20th floor shouting 'Buy Buy, Sell Sell'. It's not user driven or the productive sector driving the price up, it's the hedge funds, future traders and many others in the non-productive just play with your money and charge you do do it sector. Greed baby pure greed.

[ QUOTE ]
I'd agree that IF stainless were as strong as galvanised steel and it were the same price I'd definitely plump for it.

[/ QUOTE ]
Just as a FYI - All 10mm chain made in the EU
Grade 30 break 5000kg - available in SS or galv
Grade 40 break 6400kg - again available in both
Grade 50 break 7800kg - gain available in both.
85% of the worlds boating fleet would be on a G30 I'd guess. So some Stainless is available with big loads.
 
Re: Stainless steels

<<<< I doubt the failure quoted was primarily due to crevice corrosion - more likely fatigue, to which 316 is notoriously prone - hence some express a preference for 304, even though its corrosion resistance is lower. >>>>

Charles, if there is one failure mode that a chain can surely never suffer from, it's fatigue. I cannot conceive of any possible way that either tensile, compressive or torsional cyclic loading can be applied to a chain in anything like normal use.

Contrary to your opinion that 316 is 'notoriously prone' to fatigue, the LNG industry constructs everything from 304 or 316 stainless steel. This includes vessels, pipework and compressors at up to 40 bar pressure consuming 70 MW of power. I have yet to see a fatigue failure in any of the dozen or so plants with which I am familiar. In addition, the majority of lub oil pipework in every large pump, compressor and gas turbine in the world is made from 316 stainless steel, quite clearly without constant fatigue failure.

316 does not display the fatigue limit seen in carbon steels but its fatigue properties are perfectly adequate at up to 100 million cycles. I can think of no reason why 316 would be significantly worse in fatigue than 304. It undoubtedly fails in fatigue where the design is poor, as seen on the first Chay Blyth round the world boat forestays, but that would equally have happened in any other material. Don't blame the material for design/construction/operator errors!

Vyv
 
Re: Stainless steels

VERY interesting discussion guys, many thanks to the experts (Vyv) etc...

Again, I NEEDED new chain, SS is fine if certificated and proofed and calibrated..

I personally wouldnt go back to galv.. but, that is purely MY choice..
I rest well knowing the chain is more than up to the job..

The whole market in chain has become muddied by crappo asian chain, but not ALL asain chain is crappo, just most lol !!>
When you buy galv, you often do NOT know the origen, but you MAY respect the company supplying it.. its a lottery..

FIRST thing I did was ask for the certification, got half a metre free, took it back to the boat and gave it the once over, including cutting the links..

There are probably more out there using sheet galv then using sheet SS 316 L..

As for WHY to change, yes, galv on steel has been in practical use for 150 years, prior to that, they used rope... not many cruisers use rope these days...

Its NOT the B all and END all, just sensible IF you get the data supplied that you need...

Chains, in my humble expereince DONT give up, shackles do, nylon part rodes DO fail due to chafe...

However.. failing CHAIN itself ???.. in your dreams for the most part...

Anchors drag, (Usually a bad choice of bottom and technique - not always, but usually...) but, chain failing.. errrr nope.. not one to hit the record books..

I will stick to my SS and 20K delta on a 34 foot 8 ton boat.. works for me....
 
Re: Stainless steels

You are right it certainly isn't fatigue causing failure. I think what happens is that the chain is abraded as the the boat swings. This scratches the surface and leads to pitting and (as I understand it via elctrolysis) to crevice corrosion.

It's much the same with galvanised chain, the galvanising gets worn off and the chain starts to rust. That's curable though, corrosion in SS is fatal.

To me the bottom line is there is perfectly good high tensile test galvanised chain that can be regalvanised. Why bother with anything else.
 
Re: Stainless steels

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It's no use, I can't go on! If only I hadn't wasted my time studying for a degree in metallurgy when I could have picked up such valuable information from the Internet.

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