Stainless steel shackle corrosion

[stillbuilding]

This was a solid shackle put on an anchor 18 months ago and unused until I lifted the anchor a few days ago. One lift and we nearly lost our anchor.

Close inspection found a crack developing on the other shank too.
Obviously crevice corrosion.

Chinese item of course but suspect I would not matter whose stainless steel - just nature of the material.




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[PangurBan]

I might be wrong but I always thought that if you had a stainless steel shackle on a galvanised chain you're bound to get electrolytic corrosion.


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[JPA Cate]

Do not use s/s shackles. Spend enough to buy the tested galvanized ones. Lubricate the threads of the pin with lanolin. Mouse the shackle.

Yes, I have to agree with the implication that there's a lot of Asian poor quality stainless about these days. It's a worry.

Incidentally, in the early times of noelex's thread about "Pictures of Anchors Setting," he or his "mermaid" actually got a picture of a shackle in the process of failing. Quite amazing, actually.


Ann

[Polux]

I am more prone to the Chinese lack of quality.

A friend of mine lost the anchor and chain last year the same way.

The difference in breaking load is very big depending on the quality. For example a top of the market 10mm shackle will break at 5000kg, a good one at 4000kg a Chinese one? I don't know, they don't say but a galvanised shackle with normal (low quality) will only take 800kg.

[stillbuilding]

Well, we all agree - of course.

But the galv shackles of appropriate size never fit unless you have an end link in the chain hey!

Given that the galv shackles that do fit are usually pissy little things the temptation to go SS is there. Sigh!

Any titanium or Monel shackles available I wonder. Might be pricey but has to be better than losing an anchor.






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[Cheechako]

Yeah, that was a cheap shackle to start with. The good ones are forged and have more of a filet blending the shank to the threaded portion.
Used quality high strength forged SS for many years. They were rated much higher strength than Galv as I remember.Of course my boats didnt sit for a long time with it submerged!

[sy_gilana]

Dont mix metals down there....
Galv chain and anchor needs a galv shackle. Buy a Bull Pin on Amazon (used by construction guys on skyscrapers)
Pound it into the last link and that link will take a shackle one size larger than the chain (In my case a 5/8" pin into 1/2" chain)
Pound it till its snug, and 180 degrees of contact to the pin, it only took me 4 hits with a 2.5 Lb hammer.

[stillbuilding]

Originally Posted by Cheechako

Yeah, that was a cheap shackle to start with. The good ones are forged and have more of a filet blending the shank to the threaded portion.
Used quality high strength forged SS for many years. They were rated much higher strength than Galv as I remember.Of course my boats didnt sit for a long time with it submerged!

Well, no argument.

Fact of life though, is that it is becoming almost impossible to buy a good quality shackle (or good quality anything?) without going to specialty industry sources. Must chandler use only stock Chinese quality now.


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[Nicholson58]

As the others have stated, never mix metals. SS is lower yield than forged steel and is prone to galvanic and stress cracking. You have galvanized steel chain. Why do you want to but a piece of shiny boat jewelry down there? The fish don't care.


Below, my terminal tackle from a commercial vessel supplier. Its called a forerunner. The end shackle has an oval pin to give higher strength. Washington Chain. This is 1/2 inch. Less than 200 dollars. It exceeds the strength of my 7/16 G4 and the swivel will not be damaged going over the roller. One photo is NOT my boat - guess.

[Mark Zarley]

1/2 in galvanized BBB chain with a stainless swivel attached to a 110lb Lehman Bruce knockoff. No corrosion except on the chain in 10 yrs. 7 months out of the yr we spend on the hook. Would not think of using a light weight shackle in place of a heavy duty SS swivel. I like my brucie boy to much.

[Cadence]

Originally Posted by stillbuilding

Well, no argument.

Fact of life though, is that it is becoming almost impossible to buy a good quality shackle (or good quality anything?) without going to specialty industry sources. Must chandler use only stock Chinese quality now.


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Look for a real chandler not a retail outlet. Probably difficult to find since shipping co.s probably have a whole dept. dedicated to outfitting.

[Lepke]

As others stated, you shouldn't mix metals in salt water. Cheaper fittings are cheap for a reason. While there are standard grades, quality depends on the maker. Commonly used 304 resists corrosion in fresh water only. 316 is used in salt water environments but will pit in salt water if fully immersed.

[redhead]

This is all great information. We are just now reviewing our set up with a mind to leaving soon. It's like "Ground Tackle 101" Thanks.

[bsurvey]

we have seen this before on shackles that did not have locking wires. the pin rotates have way out then breaks the shackle

[Offshore1960]

For a high quality US made galvanized steel shackle or swivel I prefer Crosby products. Washington Chain as mentioned previously in this thread is a good source. Also most commercial fishing supply stores or ship supply companies carry them. You can set up your own fore runner with two shackles and an eye and eye swivel and it eliminates the problem not having a long link on the end of the chain.