Bonding

[jclays]

My new to me Mainship 350 has all the green bonding wire to all the thru hulls disconnected. Why would anyone be prompted to do this.

 

[Comodave]

Some people don’t believe in bonding. I am going through my bonding system and redoing it because the PO didn’t maintain it. I do like mine bonded.

 

[jclays]

These where purposely disconnected at the thru hull and the bare end safe ended with electrical tape. Before I re attach them I was trying to find out if there would be some issue that require this. I can’t think of what.

 

[Comodave]

These where purposely disconnected at the thru hull and the bare end safe ended with electrical tape. Before I re attach them I was trying to find out if there would be some issue that require this. I can’t think of what.

There should not be any reason to unhook the bonding that I can think of. Personally I would reconnect it. But before you hook it up make sure that there anodes on the hull and shaft, etc. you don’t want everything bonded without having anodes in the water to be sacrificial or it could cause some through hull to waste away. Do you have a galvanic isolator in the green ground wire in the shore power? If not I would put one in.

 

[DavidM]

There is a reasonable debate as to whether to bond or not to bond. But if the bonding wire is there, I would reconnect it. Also make sure that the engine block is the main termination point so that the prop shaft and rudder is part of the bonding system.

David

 

[SteveK]

I happen to agree not to bond thru hulls, no need, bonding just creates a current flow. Shaft is bonded to a stern zinc, but rudders are not, they do have their own zinc attached. dissimilar metal currents to protect the stainless but not to be a source for stray current flow. Self contained circle.
Shaft protectors isolate the shaft from the engine/tranny.
But each to their own thoughts.

See attached article.
View attachment Marine grounding system.pdf

 

[boatpoker]

I happen to agree not to bond thru hulls, no need, bonding just creates a current flow. Shaft is bonded to a stern zinc, but rudders are not, they do have their own zinc attached. dissimilar metal currents to protect the stainless but not to be a source for stray current flow. Self contained circle.
View attachment 109991

Metals of differing potential are not a source of stray current.

 

[SteveK]

Metals of differing potential are not a source of stray current.

correct.

 

[magna 6882]

not to hijack thread but is the green wire going from all the threw hulls the same circuit as the green wire in the 120 service panel?

 

[SteveK]

not to hijack thread but is the green wire going from all the threw hulls the same circuit as the green wire in the 120 service panel?

Yes if the green AC ground is bonded to the DC ground which is also bonded to the green bonding wire to thru hulls. Green is a color used for ground wire, unless it is a bare wire or strap

 

[CharlieJ]

A well bonded boat cannot suffer from self inflicted stray current corrosion. That is an advantage.

 

[SteveK]

A well bonded boat cannot suffer from self inflicted stray current corrosion. That is an advantage.

Charlie Johnson
ABYC Master Technician

You have my/our attention.
Care to expand this, perhaps with examples of self inflicted.

 

[CharlieJ]

@Soo-Valley
In my experience, most stray current corrosion cases are self-inflicted. In other words, the victim boat is causing the stray current that is causing the corrosion on the victim boat. There are cases of stray current migrating from another boat but they are exceedingly rare.

So, if all of the metal underwater bits are bonded together with a bonding system where each connection is < 1 ohm, no daisy chains, etc. all of the underwater metal is at the same potential. With no voltage difference between the underwater metal components, current cannot flow should a B+ connection be made to an underwater metal component. No current flow, no stray current corrosion.

Note that a bonding system is, well, another system. And like every system on a boat, there is maintenance required to keep the system functioning properly.

 

[SteveK]

B+ meaning battery positive? why/how would that occur? Does that cause swimmer's death, I thought it was AC current.
Also I thought stray current was current that did not originate at the boat and is looking to return to origin such as dock pedestal but the return path neutral or ground is open.

 

[CharlieJ]

@Soo-Valley

B+ meaning battery positive?

Yes, B+ is battery positive and B- is battery negative that serves as the return to the source of power, the battery, and to differentiate this conductor, which carries current, from the AC Safety Ground or the Bonding conductor which do not normally carry current.

why/how would that occur?

Miswiring a bilge pump float switch, chafed B+ conductor touching an underwater metal component, chafed or bad butt splice in the B+ conductor submerged in bilge water, etc.

Does that cause swimmer's death, I thought it was AC current.

AC is the cause of electric shock drowning (ESD). The purpose of a bonding system, when installed, is to distribute cathodic protection current from a hull anode to the connected underwater metal components and to protect the boat from stray current (DC) corrosion.

Also I thought stray current was current that did not originate at the boat and is looking to return to origin such as dock pedestal but the return path neutral or ground is open.

Hopefully my explanation above will clear this up.

 

[timb]

ok I'm a little worried now . my boat is out of the water it has most of the thru hulls bonded . I doubt it's a very good connection . I have reconnected where it was broken at the rudder stuffing box and where the stainless muffler was.

but there is no anode on the hull .it does have zincs on the shaft and rudder .also I'm planning on researching shaft repair for the next haul out I have some crevice corrosion at the packing.

 

[rslifkin]

My boat has done fine with everything bonded and no hull anodes. Just anodes on the shafts, rudders, and trim tabs.

 

[timb]

Shaft protectors isolate the shaft from the engine/tranny.
But each to their own thoughts.

View attachment 109991

does this imply the drive saver is good or bad? for corrosion issues.

 

[HeadedToTexas]

@Soo-Valley
In my experience, most stray current corrosion cases are self-inflicted. In other words, the victim boat is causing the stray current that is causing the corrosion on the victim boat. There are cases of stray current migrating from another boat but they are exceedingly rare.

So, if all of the metal underwater bits are bonded together with a bonding system where each connection is < 1 ohm, no daisy chains, etc. all of the underwater metal is at the same potential. With no voltage difference between the underwater metal components, current cannot flow should a B+ connection be made to an underwater metal component. No current flow, no stray current corrosion.

Note that a bonding system is, well, another system. And like every system on a boat, there is maintenance required to keep the system functioning properly.

Now THAT's clarity. Thank you, Charlie.

 

[Comodave]

does this imply the drive saver is good or bad? for corrosion issues.

It means that any hull anodes will not protect the shaft, so the shaft should have its own anode. I do not trust the transmission to be a good conductor for shaft protection anyway so I would do a shaft anode even without a drive saver.

I had drivesavers on my engines but I took them out and put a spacer in their places. With a drivesaver you can’t really get a good engine alignment and I didn’t trust the drivesaver not to break on it’s own and leave me with a problem.

 

[CharlieJ]

@timb

...I'm planning on researching shaft repair for the next haul out I have some crevice corrosion at the packing.

This is a classic case of oxygen depletion which leads to crevice corrosion. The mechanism is that the passivation film that forms on stainless steel, making it "stainless", is dependent on a fresh supply of dissolved oxygen to maintain the film. The packing gland and cutlass bearings do not admit enough oxygen rich water so there is a lack of oxygen to renourish the passivation film, anodic and cathodic areas develop and the anodic areas become crevice corrosion. The remedy is to occasionally turn the shaft, preferably by using the boat!!

 

[SteveK]

@Soo-Valley

Yes, B+ is battery positive and B- is battery negative that serves as the return to the source of power, the battery, and to differentiate this conductor, which carries current, from the AC Safety Ground or the Bonding conductor which do not normally carry current.

Miswiring a bilge pump float switch, chafed B+ conductor touching an underwater metal component, chafed or bad butt splice in the B+ conductor submerged in bilge water, etc.

AC is the cause of electric shock drowning (ESD). The purpose of a bonding system, when installed, is to distribute cathodic protection current from a hull anode to the connected underwater metal components and to protect the boat from stray current (DC) corrosion.

Hopefully my explanation above will clear this up.

Well it appears that you are an expert and others have accepted your answer.

BTW, DC electrons flow from negative to positive, yet current is said to flow + to -, go figure.
A bilge float switch should switch B+ but it really does not matter, all it does is close a circuit.
The bonding strap or wire is B- if it is terminated at the battery negative block.

chafed B+ conductor touching an underwater metal component, chafed or bad butt splice in the B+ conductor submerged in bilge water, etc. on this we agree.

This new to me boat needed 7 thru hulls replaced due to corrosion. They were bonded. and there was zinc. There was even electrolysis of the wood surrounding the thru hulls that needed repair (surveyor caught this). Like previous boats, the thru hulls will not be bonded.
Going to repost this article that I agree with which in practice has worked.
View attachment Marine grounding system.pdf

 

[boatpoker]

There was even electrolysis of the wood surrounding the thru hulls that needed repair (surveyor caught this). Like previous boats, the thru hulls will not be bonded.
Going to repost this article that I agree with which in practice has worked.
View attachment 110104

No one trained in marine corrosion will use the word "electrolysis", that is a different process that is not related to corrosion on boats. Use of that word immediately makes me skeptical of the users knowledge.

 

[Simi 60]

Black magic and I am yet to be convinced anyone knows fully how it works.

I have seen fully bonded boats with issues
I have seen boats with nothing still going strong decades old
Ours wasn't for 40 years, now has some but I think getting rid of 50% of our anodes made an improvement - to what exactly I am not sure.

 

[Comodave]

You can have too many anodes.

 

[SteveK]

No one trained in marine corrosion will use the word "electrolysis", that is a different process that is not related to corrosion on boats. Use of that word immediately makes me skeptical of the users knowledge.

"electrolysis" was my word, my bad it seemed to fit, not.

Survey says "evidence of corrosion and wood degradation and furring from stray electric current" & evidence of over zinc protection or stray current upon bonding straps and wood backing pads for thru hull", "This condition leads to fibrous deterioration of wood"

 

[Xsbank]

My boat is festooned with anodes, 20 at last count. No problems.

I thought "bonding" was going to be about when we go down to our favourite seaside pub/bar and grill with our golf buddies and drink beer and other spirits, eat chicken wings and tell tales about boating (and golfing) and never mentioning our wives?

THAT'S bonding.

 

[CharlieJ]

BTW, DC electrons flow from negative to positive, yet current is said to flow + to -, go figure.

Absolutely, any competent corrosion technician knows that to understand a corrosion problem, they must follow the electrons.

A bilge float switch should switch B+ but it really does not matter, all it does is close a circuit.

For a submersible pump, a bilge float switch incorrectly installed in the pump's B- conductor infers that the pump's windings are always energized and the carbon tracking internal to the pump will allow a current path to the metal pump shaft and to the inevitable standing water in the bilge. See Calder.

A chafed B+ conductor touching an underwater metal component, chafed or bad butt splice in the B+ conductor submerged in bilge water, etc. on this we agree.

Good.

This new to me boat needed 7 thru hulls replaced due to corrosion. They were bonded. and there was zinc. There was even electrolysis of the wood surrounding the thru hulls that needed repair (surveyor caught this). Like previous boats, the thru hulls will not be bonded.

I was unaware that your boat is wooden. Wooden boats offer difficult corrosion challenges.

The hull potential for a fiberglass boat with metal underwater components should fall in a band of -550mVDC to -1100mVDC when measured against a silver/silver chloride reference cell to ensure that enough cathodic protection current is being generated to protect said uw metal bits. Experience has shown that this wide range of protection for fiberglass boats must be dramatically reduced to -550mVDC to -600mVDC on wooden boats. If voltage more negative than -600mVDC is applied, the wooden structure suffers delignification, where the lignin of the wood is destroyed. For this reason, I do not recommend bonding the underwater metal components on a wooden boat unless a cathodic protection controller is installed in the system. And even then, serious consideration has to occur to determine if the risk of over protection should the controller fail is worth the advantages of bonding.

Survey says "evidence of corrosion and wood degradation and furring from stray electric current" & evidence of over zinc protection or stray current upon bonding straps and wood backing pads for thru hull", "This condition leads to fibrous deterioration of wood"

Your surveyor was uninformed but understood that something was amiss, which is a good thing. It would be very, very unlikely that the "wood degradation" was caused by stray current and to make that statement, a full corrosion survey would have to be made with emphasis on determining the anode/cathode couple.
The "fibrous deterioration" of the wood is the aforementioned delignification.

Hope this helps.

 

[SteveK]

Originally Posted by Soo-Valley
Shaft protectors isolate the shaft from the engine/tranny.

does this imply the drive saver is good or bad? for corrosion issues.

For me it is a good thing, it allows isolation of the engine block and all the electrics connected to it. I do not bond to B- because of this separation.
Engine internals that carry sea water have zinc pencils.
Shafts have brushes and wired to the transom zinc. rudders carry separate zinc.

This has worked previously not bonding thru hulls so when I saw the damaged ones that were replaced which were bonded, cutting that wire was done.

 

[SteveK]

I was unaware that your boat is wooden. Wooden boats offer difficult corrosion challenges.

Charlie,
I was unaware that the hull material mattered in protecting the metal parts.

Stray current. That is another one that I always thought referred to AC current.

Self inflicted. We agree that any source of B+ into the outside water will cause a problem since bonding is B-.

Bonding. I have always thought of it as dissimilar metals that create an electric current. To protect SS or bronze zinc or aluminum is sacrificed by creating a path through bonding for zinc to flow to the precious metals.

Thank you for sharing your knowledge.