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Old 15-07-2015, 15:17   #16
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Re: Stainless steel shackle corrosion

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Originally Posted by stillbuilding View Post
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!

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Not true. Get a Crosby G209A shackle. They are as strong or stronger than SS.
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Old 15-07-2015, 15:20   #17
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Re: Stainless steel shackle corrosion

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Originally Posted by sy_gilana View Post
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.
I would be worried what this did to the strength of that link.
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Old 15-07-2015, 15:28   #18
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Re: Stainless steel shackle corrosion

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Originally Posted by SVNeko View Post
I would be worried what this did to the strength of that link.
Doubt with it not being heated it would make a big difference? What are we speaking of a couple of .001.
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Old 15-07-2015, 15:43   #19
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Re: Stainless steel shackle corrosion

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Originally Posted by stillbuilding View Post
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.

Attachment 105340Attachment 105341


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Brittle fracture is the failure mode. This is what I call jewellery kit and not for structural use.

No shackle should ever fail from brittle fracture. Ductile fracture from overload sure.

Difficult to suggest a root cause other than it isn't a structural grade of stainless. No matter what the package says.

I strongly suggest only ever using shackles from the US, UK, France, Switzerland or Italy. They need to be labelled with the brand, the max load, material grade or any other provenance. Never from any asian supplier. Especially Chinese.

Anything else gets the float test. If it floats then use it...

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Old 15-07-2015, 15:55   #20
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Re: Stainless steel shackle corrosion

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Originally Posted by Cadence View Post
Doubt with it not being heated it would make a big difference? What are we speaking of a couple of .001.
Who knows. I think a 5/8 pin would fit 1/2 chain without any expanding, so maybe he had his sizes wrong.
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Old 15-07-2015, 15:55   #21
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Re: Stainless steel shackle corrosion

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Originally Posted by PangurBan View Post
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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Other way round. The zinc galv is the least noble so it should be the larger surface area.

For long term immersion you also have the issue of crevice corrosion in 3xx stainless to consider.

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Old 15-07-2015, 16:00   #22
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Re: Stainless steel shackle corrosion

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Originally Posted by leftbrainstuff View Post
Other way round. The zinc galv is the least noble so it should be the larger surface area.
Yes, with a lot of galv chain with a little SS shackle and since they are not too far apart in nobility, its not much of an issue, even though it gets trotted out here all the time.

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For long term immersion you also have the issue of crevice corrosion in 3xx stainless to consider.
Yes, this is the real issue.
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Old 15-07-2015, 16:07   #23
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Re: Stainless steel shackle corrosion

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Originally Posted by bsurvey View Post
we have seen this before on shackles that did not have locking wires. the pin rotates have way out then breaks the shackle
If this were the case there would be evidence of significant deformation.

This example is brittle fracture. Completely different failure mode.

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Old 15-07-2015, 16:42   #24
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Re: Stainless steel shackle corrosion

The SS ones I used were Nico Fico I think or Wichard. Forged and hardened stainless. I don't think they are available anymore, Something like this: I would likely use galvanized Crosby or the like today.

ZOOM [ + ]



Features

Weight 114 g

Working load 1520 Kg

Breaking load 5200 Kg = 11440 lbs.


10 mm Diameter
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Old 15-07-2015, 17:44   #25
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Re: Stainless steel shackle corrosion

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The SS ones I used were Nico Fico I think or Wichard. Forged and hardened stainless. I don't think they are available anymore, Something like this: I would likely use galvanized Crosby or the like today.
Well, forged, yes, but hardened, not likely. 300 series stainless alloys are not hardenable in general.

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Old 15-07-2015, 18:26   #26
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Re: Stainless steel shackle corrosion

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Originally Posted by Jim Cate View Post
Well, forged, yes, but hardened, not likely. 300 series stainless alloys are not hardenable in general.

Jim
I thought they were 17-4 ph? not sure. maybe not... they'd be even stronger than 11440lbs if they were maybe...
Later: Well I just ran some crude calcs and they cant be 300 series with that strength rating.
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Old 22-07-2015, 05:06   #27
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Re: Stainless steel shackle corrosion

You need a good shackle. A grade 8 galv shackle will be stronger then the chain and it will fit contrary to what was said. Crosby, Van Beest or Columbus make them.

It is not a dissimilar metal problem here, it is particularly 316 grades of stainless that are vulnerable to stress corrosion cracking. Especially corner cut no brand generic stuff shouldn't be used. Wichard make a better stainless if you must.
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