The Curse of the Mystery Mooring Chain

Perhaps this has happened to you. It has been a long passage. After several nights of little sleep, followed by a long and tricky entrance into an unfamiliar port, you finally wind your way into the anchorage. You recognize a few friends, make a short tour around the anchorage and there it is — an empty mooring ball! You pick it up the mooring pendant, secure it to bow cleats or samson post, and call it a day. Too exhausted to even put on the sail covers, you collapse in your bunk.

A few days pass, the boat’s tidy again. A couple squalls blow through – nothing dicey, but enough to make you wonder exactly what it is your precious home is tethered to. On goes the mask, the snorkel, and you follow the chain down to find – oh dear. The so-called chain is pencil thin, or a ball of rust, or connected to an old tire rim. In other words, its a disaster waiting to happen.

Look closely at the photo above sent by reader John Stone. This is just one of several links on a “mooring” that was keeping a neighbor’s boat from drifting away. Luckily, Stone was able to get down to inspect it for the owner, whose boat almost surely would have broken free in steep chop. We’d like to say this is a rare occurrence, but it is not—especially when you get off the beaten track and find yourself in unregulated mooring fields where the law of the jungle prevails. We’ve seen moorings like this in even “high-end” clubs, and for anyone who is familiar with our dozens of anchor chain tests over the years, this may come as no surprise.

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.) One particular galvanized mooring chain—an unidentified 5/16-inch “proof coil” made in China—had corroded to nearly as thin in the one above after 2.5 years.

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 site in Connecticut to our newer headquarters in Sarasota, Fla. There, 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.

Most startling was what happened to the stainless steel chain. 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 previously.

Here’s what we said about stainless-steel chain in 2007: “Corrosion is just one of the factors affecting a chains integrity. With stainless steel in particular, disregarding work hardening under real mooring and anchoring loads involves a serious leap of faith. 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.” (See “Marine Metals,” February 2007).

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