Stainless Steel Mooring Cleats

[STrctPono]

Is anyone familiar with a company who manufacturers duplex grade stainless steel mooring cleats? I'm not looking for 316 stainless steel but something like 2205. I would like to specify it on a job but can't seem to find anyone who makes it.

Any help would be appreciated. Thanks.

 

[EdStainless]

If they are cast they may be called ASTM A890-4A, or CD4MN, or J92205, and the wrought will be 2205, or S32205, or S31803.
I have seen them but don't know who makes them.

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P.E. Metallurgy, consulting work welcomed

 

[STrctPono]

EdStainless,

Thanks for the info. That does help. I will keep searching but hopefully someone is familiar with a manufacturer...

 

[TugboatEng]

What sort of tonnage rating are you looking for? I don't have a supplier but are we talking a non-rated cleat for a speed boat or a 100 ton rated mooring bit? Is your interest in duplex to avoid crevice corrosion for bolted hardware or is this a welded on structure?

 

[STrctPono]

TugboatEng,

These are 6" mooring cleats being installed on a brand new concrete ferry pier. Certainly not a 100 ton mooring bit. It's primary use is for some 65' ferry ships to tie off to on a fair weather pier.

 

[TugboatEng]

Commercial so you don't need that shiny stainless look?

Bronze cleats are available. The link says aluminum but the bronze is in there.

http://www.pacificmarine.net/construction/pier-dock-hardware/aluminum-weld-down-cleats.htm

 

[STrctPono]

No, looks are not a concern. The current cleats on the existing pier we are replacing have not held up well against corrosion. Not exactly sure what the material is but we have a severely corrosive environment due to the proximity to the ocean, heavy rain, warm tropical weather and offshore winds.

I can't say I know anything about aluminum or bronze cleats and how they compare next to stainless steel? What are the advantages and disadvantages?

 

[STrctPono]

 

[TugboatEng]

Bronze is nearly inert in sea water and sea spray. It will turn green without use (verdigris) but will not pit or waste away. It's not subject to crevice corrosion or stress corrosion cracking. Bronze will be slightly lower yield strength than 300 series stainless. the cost will be slightly more than a 300 stainless but maybe less than 2205. Provided you use the right hardware (aluminum bronze or Monel), bronze cleats will easily out last any of our lifetimes. EdStainless could perhaps fill you in on fastening options.

 

[EdStainless]

Al-Bronze and Ni-Al-Bronze are very good seawater alloys, they are commonly used in propellers.
For fasteners I would favor bronze alloys (Al-Bronze and Si-Bronze are the most common). Give these materials lower strengths these will be large fasteners.
You could use super-duplex SS fasteners, though they will be more expensive.
Make sure that there are no washers of other materials used (no steel, galv, 304/316 SS, fiber, or such).

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P.E. Metallurgy, consulting work welcomed

 

[btrueblood]

Tug, your same link, different page, lists stainless and bronze mooring cleats and bollards:

http://www.pacificmarine.net/construction/pier-dock-hardware.htm

 

[STrctPono]

Thank you Tugboat and Ed! Great information.

Ed, any concerns with embedding Al-Bronze or Si-Bronze fasteners in concrete, such as would be the case for CIP anchor bolts? I assume that they would need to separate any contact points between the anchor bolts and the rebar in the pier...

 

[EdStainless]

I have never heard of issues in embedding these alloys.
Yes isolate from rebar, make sure that they are well sealed and raised enough to prevent pooling.

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P.E. Metallurgy, consulting work welcomed

 

[STrctPono]

Thanks for all the help you two!