Electrolysis and copper bottom paint

[glcalahan]

I am having an electrolysis issue with my sailboat. Everything is new in the electrical system and also a newly rebuilt Yanmar, new shaft and prop. I have exhausted my ideas and had even installed a galvanic isolator. Now I a suspecting the Seahawk Cukote which I choose because of it's high copper content.

I know Seahawk is getting slammed but so far has been effective for me but my issue is electrolysis.

Ideas??

Regards

GC

[Sailmonkey]

Do you own a silver chloride half cell?

If not, and your loosing metal from your boat, it’s time to buy one and learn where your galvanic and or stray current corrosion is coming from.

But your certainly not suffering from electrolysis.

https://en.m.wikipedia.org/wiki/Electrolysis

[a64pilot]

It’s stray current and it’s not due to the bottom paint, it’s due to something in all that new electrical system leaking dc current to the water.
Often it’s a bilge pump, but it could be many things.
Start with buying or borrowing a half cell, then measure the current with everything on, then one at a time start throwing breakers.
Hopefully one item will cause a big drop and you have found your culprit.

[glcalahan]

Thank you!

I buy my Zincs for Boatzincs.com and I will check it out. I am having this issue without my bildge pumps wired in!! I am hard wiring as I am rewiring the entire DC side. Already finished the AC side BUT had this issue before I had even hooked up the batteries to the engine. I added grp 31 AGMs and rewired so it is even stranger than that. Electrolysis w/o anything hooked up!

So...I am responding before I read up about the silver chloride half cell. I assume it only detects.....

Thanks!!

Again...ideas??

[boat driver]

Originally Posted by glcalahan

Thank you!

I buy my Zincs for Boatzincs.com and I will check it out. I am having this issue without my bildge pumps wired in!! I am hard wiring as I am rewiring the entire DC side. Already finished the AC side BUT had this issue before I had even hooked up the batteries to the engine. I added grp 31 AGMs and rewired so it is even stranger than that. Electrolysis w/o anything hooked up!

So...I am responding before I read up about the silver chloride half cell. I assume it only detects.....

Thanks!!

Again...ideas??

is boat plugged shore side while everything is not yet hooked up?
Assuming yes-
three places to check-
1)A/C ground/neutral should return to dock- not vessel bonding when plugged into dock.If either is connected to vessel ground (zincs) then issue is either the loop or the neighbor.
2) be sure your ground and neutral are separated at panel- they should not combine till the shore side master panel-and most important inadvertently a plug or fixture was wired incorrectly- a plug being used with the hot/neutral backwards will send juice to the ground side.
3) retrace your steps and look for anything that connects/touches metal of the vessel or bonding.

Unlike automobiles that ground to the chassis, the boat grounds must return to the panel and be handled specifically with each source of A/C power and D/C power.
Personal experience includes a battery charger/inverter with a bad manufactured circuit board- it fried a number of sail drives before isolating the issue. As well, servicing a tug boat with an expensive issue- it was discovered that one entire side of the tug was wired with the grounds attached to the hull-(automobile electrician practice)- automobile battery chargers utilized full time because of price, bilge pump wires in bilge water and insulation water logged, bilge pump switches as well age and leaking.
Good luck- it really is a detective job at time as mentioned previously. Bottom paint is not the problem.
IN the thought of the zincs- be sure they have a clean connection. Many yards have painted the hull and then put on the zincs without cleaning the contacts/bolts. that would explain current looking to other bonded metals.

[Sailmonkey]

Originally Posted by glcalahan

. Electrolysis w/o anything hooked up!

So...I am responding before I read up about the silver chloride half cell. I assume it only detects.....

Thanks!!

Again...ideas??

Again, you're not experiencing electrolysis. You need to

1. get a silver chloride half cell and measure the potential to the shaft or whatever else is corroding with the shore cord disconnected. Determine if it's protected.

2. attach the shore cord, shore breaker off and measure the potential to the shaft or whatever metal is being corroded.

3. depending on the results of 1 and 2 you may need to turn on the shore power and measure with various items on and off.

Do you have a galvanic isolator on your shore ground?

I don't understand what you mean by asking if the silver chloride half cell only detects? Its a reference electrode, you use it with a multi-meter to measure galvanic potential.

[Pelican_38]

Originally Posted by a64pilot

Start with buying or borrowing a half cell, then measure the current with everything on, then one at a time start throwing breakers.
Hopefully one item will cause a big drop and you have found your culprit.

a64pilot - I understand the basics of using a half cell, but I'm not clear on what you do with the positive lead. I know you connect the negative to your DMM and connect the positive to a probe. Then do you touch the positive to the engine block, the shaft, the body of a bilge pump, a through hull, etc?

I know what I should be looking for in terms of readings, I'm just not sure exactly what the positive probe should be touching.

Thanks for any insight.

[flyingnut40]

Following

[a64pilot]

If memory serves touch it to all of the above, they should all be bonded together, except for the thru hulls, there is contention whether they should be bonded or left isolated.
Mine came from the factory bonded, so I left them bonded, but do concede the logic of leaving them isolated.

All bonded items should have the same reading, if there is a difference, then that is an issue too, most likely a high resistance in the bonding I’d assume.

But yes, the half cell merely measures what you have, but without it your shooting in the dark.
I don’t have one, I borrowed one, my since we’re wasting away quickly, as in a couple of months.
I never did find a smoking gun and came to the conclusion I was under zinc’d. My boat only had the single propeller b nut zinc, nothing else.
I have added a hanging zinc, and since then all has been well.

Incidentally I switched from zinc to aluminum at the same time.

I am not a corrosion analysts, but there are some on the forum, of course listen to what they have to say over what I said, cause of course they are trained, where I am not.

[Pelican_38]

My first boat (fiberglass) had a central bonding system which I never checked. My current boat (wood) has everything isolated and only a shaft zinc. And my next boat (aluminum and under construction) has most dissimilar metals separated with the hull grounded at the main DC negative bus. Two transom aluminum anodes and possibly two shaft anodes.

So in my case, I'd also be touching it to the engine (which is connected to the hull) as well as the hull in various locations.

My plan is to get an electrical survey while I watch how it's conducted. Then do it again for myself once I get the boat to my dock. This stuff mystifies me and is critical to get it right.

[Corrosion-Eng]

Fact: 18 years proof available. The CAUSE can be corrected, permanently. Do a Google search for marine electrolysis. Click on conquer marine corrosion CAUSE.

[sailcrazy]

another thought??? Are your zincs mounted on a rubber pad and well isolated from your bottom paint? On another thread, discussing a similar issue where the anti-foul paint is being "blown" off the thruhulls, someone noted that the original and early replacement hull zincs always came with a thin rubber "boot" (covering the bottom and about a half inch on each side/ends)on them. I was able to buy them in Asia, but have not found anything similar here in the western world. My hull zincs connect to the bonding system via the center fastening bolts......but sloppy painting/inattention managed to get the antifoul paint (with copper in it) into the zinc well, and between the zincs and the hull. I do have a half cell, and intend to use it when we return to the boat......but I'm also going to absolutely isolate those hull zincs from the bottom paint.

[glcalahan]

Actually.....my cone shaped zinc is on the end of the shaft nut aft of the prop. No paint at all. It is a bronze 'cage' that fits on end of shaft with a nut. The cone zinc fits over the bronze cage with a small SS Allen screw to secure zinc.

[Corrosion-Eng]

FACT: Stray current causes electrolysis that is a million times more corrosive than all galvanic causes. Save yourself heartache and money. Do a Google search for marine electrolysis and hit Conquer marine corrosion.

[glcalahan]

Agree....oddly, this has happened in 2 different marinas. Presence of stray current can be checked by dropping electrode in water and ground to engine block. Again....initially this happened after I splashed the boat after 18 months of rebuilding Yanmar, mast and painting. All wiring was pulled and the start battery was only connection. No bilge pumps....AND I disconnected the start battery because I was moving start battery and adding 2 house. So no connections and in 3 weeks the small cone zinc was gone. I suspected stray so I bought a 6 lb zinc and attached to shaft. Now at new marina...very upscale marina and lost another zinc. Now the batteries and ProMariner charger and galvanic isolator are connected and in place but am just starting to rewire the DC side and bilge pumps are not yet wired. It is a weird duck. I was reaching when I asked about the high copper content of the ablative anti fouling paint.

Stumped. BTW....AC wiring is done correctly.