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Old 12-27-2015, 08:49 PM   #1
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Electrolysis check for Swift Trawler Owners

A quick note that is hopefully helpful not only to other Beneteau Swift Trawler owners but others as well. The damage that can be caused with the lack of bonding of the thru hulls to a proper ground became very apparent while the boat was in Marina Del Rey where we left the boat for three months this summer during our California coastal trip.

There was excessive electrolysis damage to the packing gland raw water intakes (one literally fractured with just a hand) as well as the start of damage to all of the thru hulls which we since tied all of them with a bonding wire to a block that was then tied to the stern zinc plate. You can see the before and after shots of the engine room thru hulls and the significant amount of electrolysis in a short two month period.

There was excessive electrolysis damage to both the port and stern raw water intakes which we have replaced. The original ones are constructed with different grades of copper one being much softer and as such it received a great deal of damage.(see image). The port water intake literally broke off with just the pressure from a hand.

There is a lot of electronics and as such a significant amount of current running through the boat. The fix was fairly simple but critically important for everyone to check and think about.

Images are:
Shot of the internal electrolysis damage to the packing gland raw water intake
Engine room thru hulls (before and after)
The bonding block we contructed with bonding wire running from all of the thru hulls.

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Old 12-28-2015, 01:23 AM   #2
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Have you found the cause?
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Old 12-28-2015, 01:49 AM   #3
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Ball valves

Those through hulls and valves don't look marine. No bonding lug on the through hull , the valves look like house plumbing? What size are they. The the though bull and valve may have different threads. Pipe and straight.
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Old 12-28-2015, 02:15 AM   #4
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Those through hulls and valves don't look marine. No bonding lug on the through hull , the valves look like house plumbing? What size are they. The the though bull and valve may have different threads. Pipe and straight.
We've had some issues raised on this forum previously regarding Beneteau ST through hulls.
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Old 12-28-2015, 07:07 AM   #5
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Before blaming the builder it might pay to check the voltage in the water at that slip.

Electrolisis is usually a slow over the years process , when vast amounts of damage happen quickly its probably not from not grounding individual items.

Many boaters do not ground every underwater item on purpose , with no issues for decades.
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Old 12-28-2015, 07:12 AM   #6
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The bonding failure may be part of the issue, however I suspect it's incidental to this failure. Bonding systems connect (often dissimilar) underwater metals and, among other things, protect them with a zinc (and sometimes aluminum) anode that's also connected to the system. If the bonding system fails or the anode is depleted, then yes, galvanic (dissimilar metal) corrosion can occur.

The pinkish hue in this case, however, is a dead give away that the alloy used contains zinc (which by definition means it's brass rather than bronze), likely a significant amount of it. The pink color results when the zinc corrodes out of the alloy, in a process called dezincification, leaving behind a weak, porous copper structure.

This article on bonding systems describes how they work, and what they can be expected to do.

"Itís important to note that the soundness of the connections in a bonding system will bear heavily on its effectiveness. Because the voltage and current that such a system is called on to transport are often quite low, the resistance must be equally low. Resistance between any two points in the system must not exceed one ohm, a high standard for conductivity, indeed, and often a tall order considering so many bonding connections are located in the bilge. Bonding system connections should be periodically inspected for corrosion and fastener tension." Bonding Systems And Corrosion | | PassageMaker

While this one explains dezincification.

"Because many brass alloys contain a substantial amount of zinc, they are especially susceptible to ďdezincification,Ē whereby the zinc selectively corrodes and leaves a porous copper shell that retains its shape but has little strength. A dezincified brass propeller, for instance, can be identified by its splotchy reddish or pink coloring. Many propellers (and propeller nuts) are fabricated from so-called manganese bronze, a brass alloy, and as such are especially susceptible to dezincification. Thatís why itís so important to protect this often-substantial investment with sacrificial anodes, and to vigilantly monitor and renew them when necessary. In a conventional assembly, which combines a stainless steel alloy shaft and a brass (manganese bronze) propeller, once the anode is gone, the metal most likely to corrode is the prop. Besides dezincification, brasses are susceptible to other forms of corrosion. Ammonia, a common ingredient in household cleaners, will readily attack brass, causing it to weaken and crack; and mercury will do the same."

Beware the Brass - Professional BoatBuilder Magazine

While this one goes into additional detail about dezincification, seacocks and dezincification resistant alloys.

"Unfortunately, a huge range of alloys lies between true bronze with very little or no zinc and true brass which contains a high percentage of zinc. Two common alloys often used in marine applications are 85-5-5-5 and DZR. 85-5-5-5 contains 85 percent copper, 5 percent zinc, 5 percent lead and 5 percent silicon and can be used below the waterline. Some European manufacturers use something called DZR brass, a dezincification-resistant brass alloy. This alloy has a higher zinc composition than many other copper alloys (30 percent or more), but it also includes trace amounts of other metals meant to retard zinc corrosion or leaching. The more zinc an alloy contains, the more prone it is to dezincification, therefore, alloys with little or no zinc content are more desirable, and typically more costly. Accordingly they can be an attractive, though inferior, alternative for cost-conscious builders or do-it-yourselfers."

Seacock Installation - Seaworthy Magazine - BoatUS
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Old 12-28-2015, 08:32 AM   #7
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Thank you CeeBee for posting this. I suggest you post it to the beneteau swift trawler builders forum also. My Swift 34 is now 5 months old and we have lived on it in Florida for 3 months. Overall it has been a very well thought out boat (less a few minor issues like the sliding door catch mounting). We got caught in 9' seas from the Dry Tortugas to Key West (4' were forecast) and she handled the seas amazingly well at 8 knots. I will forward your post and photos to Beneteau to see what they have to say. I will report back. How did you attach the wires to the valves? What valves did you use to replace them? Did you have to get those from Beneteau? Thanks.


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Old 12-28-2015, 10:05 AM   #8
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Steve beat me too it. These look like DZR brass fitting commonly used on European boats. They have a limited life span and I think it's past time to replace yours.

I really don't like to see ball valves screwed onto thru-hull fittings. If the thru-hull breaks, and they sometimes do, a lot of water will enter the boat.

I suggest you replace all of your thru-hulls and install proper flanged seacocks.
Take a look at Mainesail's instructions here Replacing Thru-Hulls and Seacocks Photo Gallery by Compass Marine How To at pbase.com

I'd use Groco products to replace yours. Groco uses 85-5-5 bronze. Their fiberglass backing plates make the installation easier.
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Old 12-28-2015, 01:54 PM   #9
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Before blaming the builder it might pay to check the voltage in the water at that slip.
.
That's why I asked if he'd found the cause. I wouldn't assume anything or just replace without pursuing the cause.

However, we also have heard this problem mentioned in regards to the hardware used on this particular boat. Whether it's the problem, exacerbates the problem or whatever the situation, the more we hear of it, the more this appears to be a weakness.
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Old 12-28-2015, 05:27 PM   #10
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Beneteau and all the other Euro production manufacturers use plated brass ball valves. This is absolutely stupid and a long known problem due to the dezincification mentioned by a previous poster. TaKe a look at one ofPaul Stevens articles on this issue.

Grounding and bonding are two entirely different things for different purposes.
You should be immediately suspicious of anyone who uses the term "electrolysis" as this clearly shows they have questionable knowledge of the issue.

ELECTROLYSIS : Chemical changes in a solution or electrolyte due to the passage of electric current.

As you can see from the definition above, electrolysis is what happens to the electrolyte (water), not what happens to any metallic components. This term has come to be applied to virtually all marine corrosion but what we are really talking about are only two different types of electrically induced corrosion ......

1. Galvanic corrosion : Corrosion that occurs at the anode of a galvanic cell.

You may remember high school chemistry class where a battery was created by connecting two dissimilar metals with wire and immersing the whole contraption in salted water thereby activating magnetic fields and starting an electrochemical process causing current to flow. On a boat with bronze, aluminum, galvanized and stainless steel that are connected with bonding wires or simply touching each other and immersed in the lake...... you accomplish the same thing. The more noble metal is the "cathode", the less noble, the "anode". In this process the less noble metal gives up electrons to the more noble thus weakening the metal, otherwise known as "galvanic corrosion".

The "sacrificial" anodes on your shafts, trim tabs etc. are supposed to sacrifice themselves thereby protecting expensive metal parts. This is why it's important to keep your anodes in good condition and never paint them. let's never refer to anodes as "zincs" as anodes come in three basic materials for different water conditions i.e. Aluminum alloy, and magnesium for fresh and brackish water or zinc for salt water. This topic deserves a little more attention on it's own so take a look at Zincs, Aluminum and Magnesium Anodes.

A vessel suffering from galvanic corrosion is usually the source of it's own problem, although two vessel's linked by shore power grounds can create a galvanic cell between two very close boats.

2. Stray Current corrosion : Corrosion that results from an electrical source causing a metal in contact with an electrolyte (water) to become anodic with respect to some other metal in the same electrolyte.

In simple terms a wire touches something it shouldn't, like a faulty bilge pump float or degraded wiring lying in the bilge sending current into the water, causing one metal to give up electrons and corrode. Again any vessel suffering from this type of corrosion is likely the master of it's own disaster but the culprit could also be a neighboring vessel. This type of corrosion can can eat metals at an alarming rate. I know of one 42' motoryacht that lost both shafts, both rudders and both propellers in a space of less than two weeks.

Complicating this picture somewhat is the fact that DC can be super-imposed on your AC wiring through the common ground on board or the ground in the shore power pedestal we all share on the dock. As all vessels in the marina are connected through shorepower grounds there is potential for widespread damage. Aside from concerns of corrosion there is also potential for electrocution if shorepower cords are allowed to lie in the water let alone the fools that leave their shorepower cord plugged in at the dock while they go out for an afternoon cruise.

Recent tests have shown that AC current from shorepower in the water can also cause corrosion to underwater parts although at a much slower rate than DC. This has been a long argued issue by people who know a lot more about this than me. Ground fault protection systems, galvanic isolators, isolation transformers and impressed current systems are some of the various methods attempting to combat corrosion.

Salt water is generally regarded as a more serious breeding ground for marine corrosion as the salt makes the water more conductive however, polluted fresh water can be even more conductive with the right contaminants.
With our aging fleet of pleasure craft it's likely that at some time, less than expert hands have played with your electrical system. If your vessel is suffering from any electrical faults or unusual corrosion consult with an American Boat and Yacht Council Certified marine electrical technician with specific corrosion control training.
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Old 12-28-2015, 05:50 PM   #11
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This is also part of why I support the marinas putting in GFCI. If you can't connect, then it indicates you have a problem and you have to address it. Now, this specific problem may have nothing to do with stray current, but it is nice to know there is no stray current around, especially in your own boat.
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Old 12-28-2015, 05:51 PM   #12
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You may remember high school chemistry class where a battery was created by connecting two dissimilar metals with wire
Thank goodness I took Physics instead of Chemistry. Only one required where and when I went.
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Old 12-28-2015, 09:43 PM   #13
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Indeed, in addition to the dezincification issue, these "seacocks" appear to rely on incompatible threads, the through hull's NPS and ball valve's NPT (this incompatibility is a violation of ABYC Standards, as well as common sense), and they almost certainly wouldn't pass the ABYC 500 lb 30 second static load test. Replacement with UL approved Sea Valves (not just any UL approved valve, it must be a UL "Sea Valve") means the alloy is appropriate, i.e. little or no zinc, threads are compatible, and it's able to withstand 500 lbs of static load.

This type of corrosion can occur entirely in the absence of any outside influence, including DC stray current or a connection to shore ground via the shore power safety ground. Dezincification is essentially self-contained galvanic or dissimilar metal corrosion, with the zinc being the less noble of the two.
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Old 12-29-2015, 06:25 AM   #14
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Beneteau valve issue

I have forwarded CeeBee's photos and sutuation to Beneteau for a response from their engineers. There are no plated valves on my through hulls but I will find out what they are made of and report back
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Old 12-29-2015, 07:36 AM   #15
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"and it's able to withstand 500 lbs of static load."

Folks that simply glue sea cocks in place with no thru bolts might want to do this test.
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Old 12-29-2015, 09:23 AM   #16
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"and it's able to withstand 500 lbs of static load."

Folks that simply glue sea cocks in place with no thru bolts might want to do this test.
They're not "simply glued" as you well know. The flanges are bolted to backing plates (in my case I also used 5200 to adhere them). The fiberglass backing plates are significantly wider than the flanges and present a large bonding surface where they are epoxied to the hull. The through hulls are deeply embedded in the flanges with the same thread pattern.

In this test (using G10 vs fiberglass) shear strengths of more than 2000 lbs were observed using epoxy. Epoxy Tests & Comparison
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Old 12-29-2015, 11:29 AM   #17
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Beneteau uses Groco bronze hull strainers and Groco bronze inline marine ball valves on the Swift Trawlers. I am happy to send pics I took of my valves. I think there must be something very electrical going on with CeeBee. My anodes (zincs as called by everyone here in Florida) are in great shape after 4 plus months in the water. My diver said they show hardly any loss. I am not sure if the through hull fittings are NPS with NPT valves screwed onto them but I suspect this is the case. This is the equipment made by Groco for this application (both the through hull intake strainers and the valves that are mounted to them) which according to Groco is a proper application. They do make flanged through hull fittings as well, Beneteau opts for the threaded fittings. Beneteau hulls are very thick due to the cored construction and that may have something to do with it and Surely cost savings are important to them. I wanted a new efficient boat of this design, that I could afford. After 4 years of research there was no second candidate for us anywhere near the price range for us. I guess if you want a boat with the higher end fittings you buy a pricier boat? After I hear from beneteau I will report back. By the way, I wouldnt have any other ball material in my valves but chrome plated. There is a reason they plate them for their marine ball valves. The issues are wear and seat corrosion both of which the plating resolves.


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Old 12-29-2015, 11:46 AM   #18
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Beneteau uses Groco bronze hull strainers and Groco bronze inline marine ball valves on the Swift Trawlers. I am happy to send pics I took of my valves. I think there must be something very electrical going on with CeeBee. My anodes (zincs as called by everyone here in Florida) are in great shape after 4 plus months in the water. My diver said they show hardly any loss. I am not sure if the through hull fittings are NPS with NPT valves screwed onto them but I suspect this is the case. This is the equipment made by Groco for this application (both the through hull intake strainers and the valves that are mounted to them) which according to Groco is a proper application. They do make flanged through hull fittings as well, Beneteau opts for the threaded fittings. Beneteau hulls are very thick due to the cored construction and that may have something to do with it and Surely cost savings are important to them. I wanted a new efficient boat of this design, that I could afford. After 4 years of research there was no second candidate for us anywhere near the price range for us. I guess if you want a boat with the higher end fittings you buy a pricier boat? After I hear from beneteau I will report back. By the way, I wouldnt have any other ball material in my valves but chrome plated. There is a reason they plate them for their marine ball valves. The issues are wear and seat corrosion both of which the plating resolves.


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Definitely is something else going on and not just the fittings and I think it's crucial to find out what or replacing fittings turns into just a short term solution. On the other hand, this isn't the first time we've heard their thru-hulls questioned. Doesn't mean it's a bad boat. Just means some issues on his that need to be addressed.
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Old 12-29-2015, 12:13 PM   #19
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How did you attach the wires to the valves?


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We use hose clamps to connect the ground cable / wire to those parts without an appropriate port.


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Old 12-29-2015, 12:16 PM   #20
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If the plumbing hardware is turning pink, and fracturing, it's dezincification, that's definitive. True, zinc-free bronze does not turn pink, that too is definitive. I've encountered this many times. This is not to say a stray current scenario doesn't exist, however, regardless, zinc bearing alloys are a liability and, with one exception, should not be used. Dezincification-resistant, or DZR, brass was developed to allow zinc-bearing alloys to be used for below the waterline applications. They are, must be, embossed DZR (more detail is included on those in the link I provided in the previous post). Given the choice, however, my strong preference remains a UL/ABYC compliant bronze or glass reinforced nylon (Marelon or TruDesign) product.

The "seacocks" shown in the images are made in Europe, they are not Groco components.

The plating referenced earlier I believe refers to the outside of the valve, rather than the ball, these, the plated valve bodies, are commonly nickel plated brass, which is not suited for use as a seacock. The nickel plating prevents the components from turning green (the green, verdigris, is by the way harmless, pink on the other hand is an issue), however it does not prevent dezincification once it's breached.

If you can see threads between the valve and through hull, it lacks a flange and it's unlikely to pass the 500 pound static load test, and it's likely the threads are incompatible.

Flanges are not required for ABYC compliance, simply performance and compatible threads, the flange is a benefit that makes compliance with the static test possible. Again, a seacock that carries a UL "SEA VALVE" compliance will pass all of these tests, it's ABYC and ISO compliant.

If a seacock's flange is equipped with holes for bolts they must be used, for ABYC compliance. The bolts can either be through bolts, through the hull, typically carriage bolts, ideally bronze rather than stainless steel, or lag bolts into the backing block (backing blocks should be made from fiberglass/composite material such as GPO3 or G10, or epoxy encapsulated marine plywood, or using a proprietary product such as Groco's pre-prefabricated composite backing block, solid timber, regardless of species, should never be used as it is too prone to splitting). If the hull over which the backing block is to be installed is convex, the backing block should be "mushed" in place using thickened epoxy, creating a shim that will ensure the through hull fitting is perpendicular with the hull, and ensuring the backing block is fully supporting the seacock flange.
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