Steer Clear of Stainless-steel Mooring Chain

Posted by at 05:52AM - Comments: (7)

We had an unpleasant, although not surprising, discovery this week as we revisited the topic of ground tackle. Many readers will recall that we began a series of mooring chain tests back in 2006, with corrosion reports in 2007 and in 2008. As one Practical Sailor tester put it, the test could be described as an attempt to determine how long it took our hard-earned money to turn into a pile of rust. (As it turned out, this happened a lot faster than we expected.)

The test chains, prior to immersion in saltwater, are (from left to right): Acco proof coil, Acco BBB, Acco high test, Campbell proof coil, Chinese proof coil, Suncor stainless, and Campbell zinc-plated proof coil.

At the end of 2.5 years in the water, when we decided that no one in their right mind would trust their boat to any of the seven badly corroded 5/16-inch chains, we pulled them out for the final inspection. We found varying levels of corrosion, with 20 percent less metal remaining in cheaper Asian-made links, as compared to the chain we eventually recommended from Acco (a brand that has since been purchased by Peerless Chain Co.). The Acco Grade 30 chain, in our view, seemed to be the best balance of price and corrosion resistance in a mooring chain.

After that report, the chains got shuttled from our test sight in Connecticut to our newer headquarters in Sarasota, Fla. And as often happens when a person or company makes a terrestrial move, the mooring chains wound up in a box labeled IMPORTANT, and were promptly forgotten. The box sat in a corner of our workshop for a couple of years, re-emerged during a much-needed house cleaning and were hung from a fence in the editor’s backyard as a constant reminder that it was high time he followed up on this test. And this week (finally!), that is what we did. Using sophisticated equipment at a Tampa, Fla., facility that specializes in testing industrial cables, wire, and hardware, we applied increasing loads to our mooring chains and recorded the load data (tensile strength) until they broke.

While you will have to wait for the upcoming report for the full results (soon—I promise), one finding needs to be shared here, in Practical Sailor’s free public forum: Don’t rely on stainless-steel chain for mooring or anchoring.

Even though our stainless-steel chain sample clearly had more meat and was much shinier than our other samples at all stages of the test, it was one of the first to go in our test of breaking strength. The ease with which it broke was shocking, although we can’t say we were totally surprised.

For years, we’ve been warning sailors about the hidden dangers of stainless steel in mooring chains, lifelines, chainplates, anchor swivels, turnbuckles, rod-rigging, keel bolts—the list goes on and on. In many of these cases, we have not rejected the material, merely advocated careful selection of the appropriate grade (304, 316, 316L, etc.) and frequent inspection. Stainless steel remains the most practical choice for many other applications.

Although stainless steel is well-suited for fabricating a wide range of sailing hardware and equipment, we feel that it is a poor choice for anchor or mooring chain—and not just because it costs so much more than the usual choice, galvanized steel. One of stainless steel's biggest vulnerabilities is the work hardening caused cyclical loading, the repeated "shock" loading that an anchor chain experiences. In simple terms, work hardening makes the metal brittle. Another vulnerability is crevice corrosion, which I wrote about last year.

Here’s what we said about stainless-steel chain in 2007: “Corrosion is just one of the factors affecting a chain’s integrity. With stainless steel in particular, disregarding work hardening under real mooring and anchoring loads involves a serious leap of faith (see "Marine Metals," February 2007). Stainless steel sees so little use in high-load-cycle applications precisely because it does not hold up as well to this use as do materials with higher ferrous content. Its ever-shiny surface can actually be a disadvantage, revealing no clues to impending failure.

Bottom line: When it comes to anchor or mooring chain, what you can’t see can hurt you.

Comments (6)

Because stainless is much weaker than steel it would be nice to see the numbers compared to original break strengths or even safe load numbers even if it's your recollection of same. Were I am you cannot leave a mooring in place for more than a week. To get around that I was looking for a light chain to run from my mooring to the dock so I can easily and quickly pull up the end of my galvanized mooring chain and attach a float. I wanted same to last a long time. The info you have given is extremely helpful anyway. I recently bought a home on a bay front were the wave action was sufficient to cause my stay's (old to begin with) to fatigue fracture in 5 months fortunately no other damage occurred and am now working on getting boat lifts for my pier/dock.

Posted by: TomK | September 13, 2017 10:42 AM    Report this comment

I have never gone straight answer as to whether it is better to replace top chain with nylon for moorings. Many lobsterman Maine do so and claim that it works better and lasts longer. I would love for Practical Sailor to look at this issue.

Posted by: Mark L | October 25, 2012 3:17 PM    Report this comment

I have never gotten a straight answer as to whether it is better to replace to

Posted by: Mark L | October 25, 2012 3:13 PM    Report this comment

if: you want some real junk (stainless or otherwise) buy the trash comming out of CHINA.... HISTORICALLY CHINA HAS DUMPED not just poor chain but any other product or services. gypsum drywall, safety things like GFI'S, welded products....all just junk.....regardless of price. AND NO THIS ISNT A RECENT CASE OF "CHINA BASHING".

Posted by: Jerry B | October 24, 2012 12:44 PM    Report this comment

As I sail Lake Champlain for more than 20 years now, like every year at this time of the season, I have to remove my mooring buoy from the water. This yeat, I was surprise by the fact that my mooring chain, for the first time, was totally recovered by zebra mussels. As it is originaly a 3/8'' chain it was now about 3'' thick.

I am wondering if the zebra mussels will have an effect on the strenght and life time expectation of the chain. Do you have information about that ?

Posted by: REJEAN F | October 24, 2012 11:04 AM    Report this comment

While I understand the comments and concerns with SS chain. NOT all SS chain is made equal.
We use WASI German made chain that is Lloyds approved and have had no problems or indications of excess corrosion, creep. Each link is stamped. We've used the chain extensively for the last 12 years cruising on our Swan 53 in both the Eastern Caribbean and New England everyear. We always anchor rather than grab a mooring.
Our Chain is 3/8's BBB and a 66 lb Bruce (original). We wouldn't trade our ground tackle for anything!
Main reason for using our 310 feet of chain is our anchor locker isn't deep enough for Galvanized chain to flake as it's recovered. Stainless Chain flows like hot butter.
Not all Stainless is made alike is all I'm saying.

Posted by: Robert B | October 24, 2012 10:49 AM    Report this comment

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