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Master Mariner
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Discussion Starter · #1 · (Edited)
Cleaning our good old USA manufactured chain yesterday, I noticed this pitting. This chain is less than a year old, the galvanizing is almost nearly gone and now this.
Have any of you seen anything like this on chain before? Could this be casting flaws, little bits of impurities in the manufacturing process? It looks like nothing so much as little holes left by small bugs; chain mites.
I forgot to mention that this chain is being used daily as my anchor chain.
 

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bell ringer
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Do you have an electric windlass, how are the ground connections on it? That's some impressive pitting corrosion.
 

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The quality of chain today is not what it used to be, but that's really bad for only a year. I've been pretty happy with Acco mooring chain, but still only get 2 or 3 years out of my upper chain.
 

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Old as Dirt!
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Do you have an electric windlass, how are the ground connections on it? That's some impressive pitting corrosion.
I agree with Don. That certainly looks like erosion due to electrolysis. Our anchor chain is 12+ years old and other than some wear, there is no erosion whatsoever. From those photo's I'd guess that windlass is "hot".

FWIW...
 

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Interesting that the chain is black. Those pits are identical in appearance to those often found in the bottom of large oil tanks that have been storing high heavy oils. They can form in 2 years if...

Electrolysis is present or if there is some chemistry that causes a differential (layers in the tank bottom sludge) in oxygen concentration. Have you been anchoring in some manner of smelly mud? Have you been anchoring in the same spot for extended periods?

How do your shaft zincs look? If they are fine, electrolysis seems less probable. If they are shot....
 

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Interesting that the chain is black. Those pits and the coloration are identical in appearance to those often found in the bottom of large oil tanks that have been storing heavy oils (I do corrosion studies as part of my day job). They can form in 1-2 years if...

Electrolysis is present or if there is some chemistry that causes a differential (layers in the tank bottom sludge) in oxygen concentration. Have you been anchoring in some manner of smelly mud? Have you been anchoring in the same spot for extended periods?

How do your shaft zincs look? If they are fine, electrolysis seems less probable. If they are shot....
 

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Master Mariner
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Discussion Starter · #7 ·
Interesting that the chain is black. Those pits are identical in appearance to those often found in the bottom of large oil tanks that have been storing high heavy oils. They can form in 2 years if...
Electrolysis is present or if there is some chemistry that causes a differential (layers in the tank bottom sludge) in oxygen concentration. Have you been anchoring in some manner of smelly mud? Have you been anchoring in the same spot for extended periods?
How do your shaft zincs look? If they are fine, electrolysis seems less probable. If they are shot....
Unfortunately, the zincs are also a year old and in need of replacement just on general usage. We've been anchored in Prickly Bay, Grenada for a couple of months and have not had this problem in the two previous years here, with different chain. The way it is so hit and miss along the chain, but mostly concentrated on one side of the links affected, would push my thoughts more toward casting flaws; one would think electrolysis would be more of an equal opportunity metal muncher?
As you may have noticed, the galvanizing is long gone as well, worn right off.
 

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Unfortunately, the zincs are also a year old and in need of replacement just on general usage. We've been anchored in Prickly Bay, Grenada for a couple of months and have not had this problem in the two previous years here, with different chain. The way it is so hit and miss along the chain, but mostly concentrated on one side of the links affected, would push my thoughts more toward casting flaws; one would think electrolysis would be more of an equal opportunity metal muncher?
As you may have noticed, the galvanizing is long gone as well, worn right off.
Not casting flaws; wire is drawn, not cast. However, the bending/forming of the wire causes stress and the stress accelerates corrosion.

Brand and grade? The corrosion pattern to me suggests low temper, but I'm guessing.

Were parts buried and parts exposed? Patches of grass (I'm not clear on what you mean by hit-or-miss)?

Judging from the black color, I wouldn't blame the chain; there is something else going here.
 

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Master Mariner
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Discussion Starter · #11 ·
Not casting flaws; wire is drawn, not cast. However, the bending/forming of the wire causes stress and the stress accelerates corrosion.
Brand and grade? The corrosion pattern to me suggests low temper, but I'm guessing.
Were parts buried and parts exposed? Patches of grass (I'm not clear on what you mean by hit-or-miss)?
Judging from the black color, I wouldn't blame the chain; there is something else going here.
Never buried, little grass. Whatever it is is not uniform nor is there any pitting on the anchor, galvanized thimble or chain hook for the snub.
There is some concern that what was sold to us as USA manufactured hot dip galvanized bbb marine chain was actually electroplated chain of a lesser quality, which may follow your low temper theory. We'll check the zincs tomorrow, but I'm not sure they'll show us much. Pulled the anchor today and checked the whole length and its definitely not uniform and does not seem to be related to association with the mostly sand bottom, or electrolysis.
 

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What kind of bottom? Mud or rocky? To me it looks like the chain is wearing again something likes rocks or coral. Just the outside edges of the links, the galvanized is worn off and steel is pitting. Was it a hot dipped chain? Do you know exactly what you bought for chain and from who?
 

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Iron fastenings turn black and dissolve in the presence of copper .Not very noble of it ,eh? Sounds like an electron exchange of some kind. First the zinc , then the pitting. If the winch isn't hot , maybe a claim for mineral rights.
 

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If the pitting is not even along the length of the chain, maybe the problem is in your chain locker. The chain may have a tendency to coil more or less the same way each time, so that the same parts come in contact with something in there.
 

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Master Mariner
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Discussion Starter · #15 · (Edited)
Chain with the pitting hasn't been in the chain locker in months, except for a few hours here and there. Bottom is heavy sand, pebbles and broken shell, it seems.
Pulled the anchor yesterday. No pitting or corrosion on snub line thimble or chain hook, both galvanized, nor any on the anchor. I'd assume if it was electrolysis it would be everywhere? Much worse on the chain that moved around; 25' to 75', almost none on the first 25', which would be more "in"the bottom, and none at all on chain that wasn't in the water. I'm befuddled.

UPDATE; Dove under the boat and all zincs are in about the shape they should be. No excessive wear or less than normal. Color me double befuddled, now.
 

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Again, that sound like perfect wear and tare from the bottom. when there is little wind the last 25' of chain is getting dragged around the bottom. And the outside facing surface of the links, the galvanizing is wearing off. Bare steel will start pitting very fast.

If it were galvanic corrosion it would not only be on the outside surfaces.
 

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True ,the first zinc to go would be on the outside surfaces and the inner surfaces still protected. I've pulled mooring chains ,been in use for 30 years and never seen local pitting like that. I did see similar stuff when my Dad fixed 2 generators to make 24v in series. for his first hf radio. One was 12 v below ground which it saw as + in series with the normal one so 24v, get it? Radio work real good but boat fairly bubbled Not to suggest your wiring is that haywire but sounds like pumping electrons down (or out of)the chain to me. Only other is a manufacturing defect. Either way ,don't trust that bit of chain.
 

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If you bought it in the Islands it may well not have been what it was marketed as. Even here in the US I have seen cases of cheap Chinese metal products of very suspect quality sold as made in US. I had a temp at where I work state that the last job he had was at a major bearing manufacturer and his job was to grind off the "China" stamp off of bearings and put them in made in USA boxes. I can only imagine there is more stuff miss marked creeping into the supply chain in the islands. This is why knowing your supplier is important on anything to do with critical systems. If they can make a watch that fools jewelers, it does not seem far fetched that there could be counterfeit chain on the market.
 
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