Anchor and rode: How rusty is too rusty?

[NPCampbell]

Originally Posted by psp2psp2

I opened up my wallet for 10mm stainless chain. We anchor a lot and sometimes for days at a time. The chain still looks great after years of use and I consider it one of the best equipment purchases I ever made. So how much rust is too much? I would say any.

Here’s a link to some video

https://youtu.be/zlO8vAowYgE

What grade of stainless is that? I've only read about duplex holding up below the water line.

[MartinR]

Stainless has many advantages, it does not rust easily, it stacks better in the chain box and it tends to run smoother through the windlass and is stronger.

The reason we do not use stainless is very simply the failure mode. Stainless breaks without a warning. A small manufacturing fault will have big consequences. Also, stainless does not hold up well under water.

[Mike OReilly]

Originally Posted by MartinR

...The reason we do not use stainless is very simply the failure mode. Stainless breaks without a warning. A small manufacturing fault will have big consequences. Also, stainless does not hold up well under water.

This has always been my understanding.

[NPCampbell]

Originally Posted by MartinR

The reason we do not use stainless is very simply the failure mode. Stainless breaks without a warning. A small manufacturing fault will have big consequences.

Not all stainless is susceptible to stress corrosion cracking, only austenitic.
Duplex, on the other hand, is incredibly corrosion resistant and most grades have a higher yield strength than BBB/30 or grade 40 galvanized anchor chain.

Cost is the major reason why it is not used.

[conchaway]

It's too rusty when it breaks loose in heavy weather-- hope this helps.

[danfarrell]

I took a good look at the chain and anchor - it's actually in perfectly fine shape. There's some rust, but it doesn't seem to have gotten to the point of flaking off and for the price new chain probably makes more sense than regalvanizing 40 feet of older stuff. The last foot or so of chain is a lot more rusty than the remainder, so I may just remove it as suggested.

Thanks for the advice folks. I appreciate the perspective.

[Tillikum]

Throw it into a cement mixer with some sand and water and tumble until clean, then wash off, dry with a tiger torch until no moisture comes off and too hot to touch, then dunk in linseed oil and let dry. Paraffin wax is good as an alternative to the linseed oil. Bit of a PITA though, unless you're stuck somewhere you can't buy new chain.

[mako]

Originally Posted by Tillikum

Throw it into a cement mixer with some sand and water and tumble until clean

Sorta like cleaning cartridge cases with corn cob in a tumbler. I would think dry would be more effective than with water though. Has got to make a hell of a racket!

That's a good idea Tillikum, you homicidal killer whale.

[MicHughV]

the thing about rust is this....
eg...a 1" thick plate can throw off about 10" worth of " rust"...so just seeing a "rusty' surface is no reason for concern....

but...plenty of places around that can re-galvanize chain for you...

[thinwater]

The best vetted and very conservative ABYC ground tackle standard says give these loads. I doubt anyone has a story of a chain in good condition meeting ABYC table 1 breaking.


The OP's boat is 30', so that is WLL of 1400 pounds for a storm anchor. 1/4-inch grade 30 has a WLL of 1300 pounds. 1/4-inch G43 chain has a WLL of 2600 pounds. Get 1/4-inch G43 chain, which will fit the existing windlass and have 185% of the required strength. Done.


Regarding SS chain, the current wisdom is by the time crevice corrosion and fatigue are considered, SS has the same working life as galvanized. You will need to replace it while it still looks good... which you won't. Just sayin'.


As for anchor size, I'd rather not joining that dance. Try what you've got. If you don't like it, get a new generation anchor and go up one size. You will have doubled your hold and increased reliability by at least 10 times.

[MicHughV]

in over 40 years of sailing and engineering, I have only come across duplex stainless steel one time, it is prohibitively expensive, and not many places around that are qualified to weld it..and even so.....weld splatter that isn't cleaned off will " rust".....

I have a " collapsible" stainless steel northill anchor, now approaching 30 years old, still in remarkable condition..no, it's no for sale...

[MicHughV]

safety factors for chain are usually 5:1....so some margin for error.....but it only takes 1 bad link to make the entire length of chain dubious...

[MicHughV]

the shrimp boats around here all use the northill.....usually galvanized....could not say why they prefer it...their anchors and chain always seem really rusty to my eye, but it doesn't seem to bother them....

[thinwater]

Originally Posted by MicHughV

the shrimp boats around here all use the northill.....usually galvanized....could not say why they prefer it...their anchors and chain always seem really rusty to my eye, but it doesn't seem to bother them....

Where is that?

[mako]

The Northills are easy to fabricate and many of the ones I’ve seen on fishing boats certainly look it