Stainless Shackles on Galvanized Anchor Chain

[Hermit Scott]

I bought 30' of hot dip 5/16" high strength chain at Home Depot. I also bought a couple of stainless steel shackles. I used one on the anchor and one one the end of the chain where the rope tied to. I anchored the boat out away from the dock to prepare for a hurricane. I left it there for 3 weeks or so. When I pulled the ground tackle up, the brand new chain was rusted almost completely. The anchor was already pretty rusty.
Is this normal? Could the stainless have caused the rapid deterioration of the galvanized coating. I just bought a new 33 lb. claw. It is also hot dipped and I don't want it to turn out like the chain. Should I buy gavanized shackles instead of stainless? Should I mount a zinc to the anchor/chain?

I walked the docks and most people with a 30' plus boat had a plow or a claw or they had both. Also popular is the fortress type anchor. The 33 lb. claw is 2 sizes up for my 30' boat.

 

[Ross]

I will take your word for the rust if you scrubbed it a little to make sure it wasn't stain. I rather doubt that the SS shackles were the cause.

 

[sailingdog]

You shouldn't use stainless steel in an anchor rode IMHO. Stainless steel doesn't tolerate low oxygen conditions, like being buried in mud, very well. It also will react to the zinc on galvanized steel and cause the zinc layer to be eaten away more quickly than it should be, drastically shortening the life of the chain.

Generally, as a rule, you shouldn't mix different types of metal under water.

Also, the chain at Home Depot isn't the same as marine anchor chain. IMHO, the galvanization isn't as good, and the chain will not last as long.

 

[Ross]

Sometimes Home Depot sells Campbell or ACCO chain but the Chinese look alikes are to be avoided.

 

[BrianW]

I had the exact set up you discribed. After 1 year in the anchor locker in a salt water environment, two links of the galvanized anchor chain were severely corroded. After I hit the links with as hammer to clean it off, half of the metal came off. I simply hacksawed off the two links and replaced my expensive stainless shackle with a much cheaper galvanized one. BrianW

 

[Guest]

Anchor chain

I use industrial grade 5/16th inch high test anchor chain on our boat, which HD normally does not carry. We keep our 1991 model year boat in the water year around and the chain shows little to no signs of corrosion.

HD normally sells proof coil (low grade) and BBB better, but not as strong or corrosion resistant as high test (grade 40) or grade 70. I would also question HD's product country of origin. I try very hard to stay away from off shore manufactured products.

The SS shackle should have little to no effect on the galvanized chain corrosion.

Terry Cox

 

[sailingdog]

Given the extreme difference on the galvanic series, I would disagree. The stainless steel shackle will affect the zinc galvanization on the links closest to it at a minimum.

The SS shackle should have little to no effect on the galvanized chain corrosion.

Terry Cox

The galvanic series as found on this website:

The galvanic series (or electropotential series) determines the nobility of metals and semi-metals. When two metals are submerged in an electrolyte, while electrically connected, the less noble (base) will experience galvanic corrosion. The rate of corrosion is determined by the electrolyte and the difference in nobility. The difference can be measured as a difference in voltage potential. Galvanic reaction is the principle which batteries are based on.

Galvanic series (nobler higher)

The following is the galvanic series for stagnant (that is, low oxygen content) seawater. The order may change in different environments.

GraphitePalladium
Platinum
Gold
Silver
Titanium
Stainless steel (316 passive)
Stainless Steel (304 passive)
Silicon bronze
Stainless Steel (316 active)
Monel 400
Phosphor bronze
Admiralty brass
Cupronickel
Molybdenum
Red brass
Brass plating
Yellow brass
Naval brass 464
Uranium 8% Mo
Niobium 1%
Zr
Tungsten
Stainless Steel (304 active)
Tantalum
Chromium plating
Nickel (passive)
Copper
Nickel (active)
Cast iron
Steel
Lead
Tin
Indium
Aluminum
Uranium (pure)
Cadmium
Beryllium
Zinc plating (see galvanization)
Magnesium

 

[Hermit Scott]

The anchor is cast iron also, no doubt made in china. I can have it galvanized here in san antonio if there is a problem with it. I am not sure if they can gavanize the chain without making it one piece. All the things I have had galvanized were non moving parts. The chain was high test. The 5/16" is much stronger than low test 3/8".
I am going to the boat tomorrow. I will stretch out the chain and take some pics.
Also does any one know about aquamet 17. The shaft I have is aquamet 17. I need to know how long it will last in salt water. I don't mind replacing the shaft if it goes bad. I already bought it and now can't return it. The bigger headache will be replacing the cutlass bearing if the shaft keeps getting corroded and wears it away.
saildog-thanks for the chart

 

[Ross]

Find a small piece of SS and a small piece of galvanized steel and connect them to a digital volt meter and immerse them in sea water or a tablespoonful of salt in a pint of water and check the voltage. then use two oieces of galvanized steel for the same thing . The greater the voltage, the more corrosion.

 

[Ron20324]

There are companies that re-galvanize chain, but due to the process they often have a minimum- 500 feet, as I recall. That means maybe you can gather some other people at the dock if you need to get enough for the minimum. As to stainless shackles, you wouldn't use them on a permanent mooring, but a rode used once in a while should tolerate the limited air starvation. After all, they do make stainless anchors, so why not stainless shackles? All the same, I'd get the galvanized shackles if buying new. Get the next size up from your chain size. There should be a "grade" stamp on each link of your chain. Does it say 4G?

If your anchor is rusting, get the spray-on rust neutralizer, which is what I have done for my CQR. Then you can use the spray-on galvanizer, which I have not applied yet- and may not.

 

[Guest]

SS shackle

Thanks for the reply to my comment about SS to galvanized corrosion, or lack thereof. How do you explain the absence of corrosion between a SS thimble and a galvanized shackle that is immersed in sea water for an extended period of time? Just curious, because it is one thing to cite numerous technical references and quite another to actually observe an outcome between dissimilar metals.

Terry Cox

 

[Ross]

Thanks for the reply to my comment about SS to galvanized corrosion, or lack thereof. How do you explain the absence of corrosion between a SS thimble and a galvanized shackle that is immersed in sea water for an extended period of time? Just curious, because it is one thing to cite numerous technical references and quite another to actually observe an outcome between dissimilar metals.

Terry Cox

Well Sir,
I invite you to register and become a member of our bumbling forum. There are many things that I can not explain but wonder about. Are the shackles and the thimble of the same alloy as the ones in the problem cited by the OP? As to proof coil chain being low grade I suppose you could call it that but one purchases the tools needed to do a job. More logs have been hauled from forests and more stuck vehicles pulled from the mud with proof coil chain than with grade 40 or 70. In the world I live and work in if 3/8 proof coil chain isn't strong enough we go to 1/2 inch.

 

[Roger Long]

Also does any one know about aquamet 17. The shaft I have is aquamet 17. I need to know how long it will last in salt water.

It won't last very long in salt water if the boat just sits and the water doesn't circulate so it becomes deoxygenated. You're in a pickle now. You'll have to go out and sail every weekend.

 

[Guest]

Ground tackle

Hi Ross, thanks for the invite to become a registered member. I was a long time registered member, but for a variety of reasons have decided to participate as a guest. I hope that does not diminish my role as a willing contributor and participant.

Regarding the different grades of chain, perhaps proof coil chain works well for your purposes, but for our marine application corrosion resistance plays an important role. I am not a chain expert, but I have consulted with them. The people who make these chains tell me that proof coil is a much lower grade of chain than grade 70. Lower grade not only has a lower working strength, but it is also less resistant to corrosion; all else being equal.

In our case the windlass gypsy that Hunter installed on our boat dictates 5/16th inch grade 40 high test. Anything else will not work. One thing I can also say about the corrosion resistance is the 1991 installed chain has spent considerable time in sea water with virtually no signs of corrosion.

As far as the alloy differences between the thimble and shackle, I can't even tell you the country of origin for sure since the shackle has been on the boat since it was built by Hunter in 1991 and the retailer is pretty sure the thimble is US made.

Terry Cox

 

[Hermit Scott]

I sent my wife to pick up the material for the shaft. I told her to ask for 19, they gave her 17. I think it is part of their repeat business program. When I asked him about it, he said they charge $10/pound for 19 and only $6/pound for 17. I was like OK I will gladly give you $50 more bucks for a 19 shaft!
Guest-I guess since you don't believe in the corrosion caused by dissimilar metals you have no zinc on the shaft of your boat? Are you seriously questioning the process? It seems to me to be one of those things that's quite well documented. But sometimes it takes more to believe. I still don't believe gravity works over an infinite distance, and that's supposed to be one of those things that's proven also.

 

[Ron20324]

Bear in mind that for almost any given anchor windlass there is available two or three different gypsys to handle different rode sizes. For example, if you want hefty lifting power but not high chain cost, get a 1000 windlass and an extra 1/4" gypsy.

 

[Guest]

Corrosion

Hermit Scott, I do not recall ever saying that I believe that corrosion does not occur between dissimilar metals. I can cite at least one experience with SS fasteners in aluminum. And yes I do install fresh zincs on our prop shaft every year.

My earlier comment had to do with a SS thimble connected to a galvanized shackle and after long periods in sea water why there was no evidence of corrosion. Perhaps you would care to explain? I cannot.

Ron20324, it would seem a bit unorthodox to rig a boat with a variety of gypsies and rode sizes, don't you think? Your advice may have merit, but since our current gypsy and rode size has met our needs in hundreds of anchoring and wind conditions, having multiple ground tackle choices would be akin to having a standby propulsion engine just in case we needed an engine with more horsepower to meet some unforeseen sea state. Do you have multiple ground tackle choices on your boat, aside from a spare anchor that is?

Terry Cox

 

[Hermit Scott]

What is a long period? Where are these parts that you are talking about? Brackish or middle of the atlantic? Has the stainless part been on other galvanized parts before? What kind of stainless? There are too many variables for anyone to explain with certainty.

 

[John]

Anchor Swivels

Since it is recommended not to use stainless shackles, what do the experts here have to say about using an anchor swivel (which only comes in stainless, as far as I know)? I was told that this is the only way to get the anchor up over the bow roller smoothly. Is that wrong?

 

[Ron20324]

Ron20324, it would seem a bit unorthodox to rig a boat with a variety of gypsies and rode sizes, don't you think?"

""Your advice may have merit, but since our current gypsy and rode size has met our needs in hundreds of anchoring and wind conditions, having multiple ground tackle choices would be akin to having a standby propulsion engine just in case we needed an engine with more horsepower to meet some unforeseen sea state. Do you have multiple ground tackle choices on your boat, aside from a spare anchor that is? Terry Cox

Actually, long-distance(world) cruisers do take different gypsies for their windlass since not all sizes of chain are available everywhere. If you lose your chain rode in un-retrieveable water depths, you might HAVE to buy BBB at the Tonga 7-11 to replace that G4- or do without.

I was not saying to have ALL the options. The windlass will come with one gypsy(no options), so the second would be "EXTRA" cost. Just when initially building your anchoring system, pick the pieces up front that suit your needs and build the system on that. I do have three or 5 anchors and different lengths/thickness of rope rode and chain. I bought the heavier 1000 windlass, but I figured I only needed the light 1/4 chain , 1/2 rope gypsy of the 700 unit, so bought if for $80. A freebie CQR 35 made me upsize the rode to match the 1000. With the additional rode expense, the CQR was not exactly a "freebie".