For my mooring I have galvanized chain and a stainless swivel shackle attached to it just under the buoy. I am in fresh water. I am wondering how long I can expect this system to last. I understand that mixing metals is less than ideal for underwater applications but I could only find a stainless swivel shackle. I am curious how big of a deal this will be in a cold, fresh water lake. How much of a hurry should I be in to replace it with a galvanized swivel?
Mixing metal in a mooring
- Thread starter Adam D
- Start date
I don't think the mixed metal, galvanized steel and Stainless steel is much of an issue. However, SS is prone to stress hardening and sudden failure without any warning.
Is Stainless Steel Really the Best Metal for Use in an Anchor? - Inside Practical Sailor Blog Article
Is Stainless Steel Really the Best Metal for Use in an Anchor? - Inside Practical Sailor Blog Article
It it were me, I'd just keep an eye on it, and see what happens. If you notice any corrosion, just swap it out and chalk it up to experience. Probably take a loong time.
If you were leaving the boat on the mooring for long periods unattended, I might think differently.
If you were leaving the boat on the mooring for long periods unattended, I might think differently.
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I'll also add - you can find a mosquito's ear on Amazon now-a-days. If it's going to constantly worry you in the back of your mind, it might be less stress just to replace it.
We've used code 70 truck chain and stainless fittings for years, and the average lifespan seems to be around 8-10 years. At the point the whole works gets tossed and start again.
Your lake isn't much different from ours.
Galvanized doesn't buy you anything. It's not about reaction or corrosion, it's about the chain rubbing against itself and scraping the coating off.
Your lake isn't much different from ours.
Galvanized doesn't buy you anything. It's not about reaction or corrosion, it's about the chain rubbing against itself and scraping the coating off.
Nope!
If you stay anchored by the"hook" for years. Still no biggie.
For reducing the chain zinc galvanization loss [meant for dry anchor storage] attached a "drop zinc" clamped to the submerged anchor chain. SS swivel is what I would choose.
Drop Zinc
Jim...
PS: I use my Drop Zinc in transient marina's berths to protect my entire boat. I connect it through a port light to the Engine to protect my shaft zincs.
That is why I said "Nope!" and "no biggie"
Even Stainless cracking takes Saltwater.
Jim...
Thanks guys. Longest my boat is unattended is maybe a week at a time. Then I pull it out of the water when the rowdy winter weather comes. I think I'll just leave it and check on it regularly.
Interested about stainless cracking in saltwater vs freshwater. Will stainless not be prone to breaking without warning in freshwater?
That is why I said "Nope!" and "no biggie"
Even Stainless cracking takes Saltwater.
Jim...
Indeed. I wasn't trying to stir the pot, some of the historical posts would have major infrastructure and an hourly inspection.
The way we've been doing it with truck drums as the anchor, the chain is loosely attached to one drum, the chain pulled taught and the rest of the drums slid down the chain. What this does is remove the wear factor at the lakebed. The only real wear is at the link to the ball. When that link shows wear, the whole works is replaced. While this may not work everywhere, it's worked exceptionally well out here.
The way we've been doing it with truck drums as the anchor, the chain is loosely attached to one drum, the chain pulled taught and the rest of the drums slid down the chain. What this does is remove the wear factor at the lakebed. The only real wear is at the link to the ball. When that link shows wear, the whole works is replaced. While this may not work everywhere, it's worked exceptionally well out here.
SS corrosion issues are present when the SS is exposed to a wet oxygen deprived environment. SS is stainless because it forms a light oxidation that prevents rust. If the SS is wet and in an oxygen deprived environment, the metals within the SS react and cause crevice corrosion. This is an issue with chainplates and fittings where the is insufficient water circulation keep the water oxygenated.
SS can work harden and then fail without warning. Some argue (check Practical Sailor for a bunch of articles on this) that swivels, anchors and chains made of SS are subject to work hardening. The SS becomes brittle and then fails. There is no corrosion or stress cracks, so there is no warning. Thus their recommendation against using SS shackles, chain, and swivels on ground tackle.
There are many alloys of Stainless Steel and many have no Stress Crack Corrosion [SCC] problems.
Anchor swivels, who spend 90% of their life in the anchor closet, have plenty of Oxygen.
At normal water temperatures... 316 SS is wonderfully resistant. High Nickel content metals like Alloy 20 are the industry standard for NO SCC.
One of @Maine Sail favorites for Saltwater marine shafts is...
Aquamet 17
Cheaper than Alloy 20, probably from the reduced Nickel content.
You @Adam D , should have no SCC to worry about in fresh water.
Jim...
Anchor swivels, who spend 90% of their life in the anchor closet, have plenty of Oxygen.
At normal water temperatures... 316 SS is wonderfully resistant. High Nickel content metals like Alloy 20 are the industry standard for NO SCC.
One of @Maine Sail favorites for Saltwater marine shafts is...
Aquamet 17
Cheaper than Alloy 20, probably from the reduced Nickel content.
You @Adam D , should have no SCC to worry about in fresh water.
Jim...