Neighbor dumping raw AC into water?...what to do?

[bene505]

I wonder if the offending boat is getting zinc build-up in all his exposed metal? I imagine there's electroplating going on. And zinc (from surrounding boats) is being amply supplied into the salt-water solution around his boat.

Regards,
Brad

[fstbttms]

Originally Posted by bene505

I wonder if the offending boat is getting zinc build-up in all his exposed metal? I imagine there's electroplating going on. And zinc (from surrounding boats) is being amply supplied into the salt-water solution around his boat.

In 17+ years and over 20,000 service events, I have never heard of or seen this happening.

[senormechanico]

With all the talk about over and under zincing, nobody has mentioned how much voltage there should or should not be impressed on the underwater metals to be protected.

I've always noticed on my boat that with a new zinc, I get -0.7 volts on the bonding system.
When the zinc weakens to less than 0.5 volts, I replace it.
At that point, it's usually porous and noticeably smaller.
On my previous boat, I used a slab zinc wired in series with a 20 ohm wirewound potentiometer which went to the bonding system.
I also had a permanently mounted silver electrode on the exterior of the hull.
With a permanently calibrated and mounted meter, I could push a button to read the differential voltage between the electrode (a 90% silver US dime) and the bonding system.
I could then adjust the potentiometer to read -0.550 volts to protect the underwater metal without using excessive zinc.
The system worked great, and I only had to replace the zinc every four or five years, while the MaxProp zinc (shaft isolated) needed to be replaced every year.

An interesting side note, the adjusted voltage dropped precipitously while underway, but returned to normal levels as soon as we were anchored.
I have no idea why.

[s/v Jedi]

Yes Steve, there are even systems that automate what you created! But I have only heard of mega yachts using those so they will be expensive.

ciao!
Nick.

[senormechanico]

I made mine out of my electronic junk box for a couple of dollars.
These days, just the dime is worth about $3 !

[s/v Jedi]

Originally Posted by senormechanico

I made mine out of my electronic junk box for a couple of dollars.
These days, just the dime is worth about $3 !

Yes I know

This active protection is called "Impressed current cathodic protection (ICCP) " and when you search it on Google, you get all the info

cheers,
Nick.

[hummingway]

Originally Posted by senormechanico

With all the talk about over and under zincing, nobody has mentioned how much voltage there should or should not be impressed on the underwater metals to be protected.

I've always noticed on my boat that with a new zinc, I get -0.7 volts on the bonding system.
When the zinc weakens to less than 0.5 volts, I replace it.
At that point, it's usually porous and noticeably smaller.
On my previous boat, I used a slab zinc wired in series with a 20 ohm wirewound potentiometer which went to the bonding system.
I also had a permanently mounted silver electrode on the exterior of the hull.
With a permanently calibrated and mounted meter, I could push a button to read the differential voltage between the electrode (a 90% silver US dime) and the bonding system.
I could then adjust the potentiometer to read -0.550 volts to protect the underwater metal without using excessive zinc.
The system worked great, and I only had to replace the zinc every four or five years, while the MaxProp zinc (shaft isolated) needed to be replaced every year.

An interesting side note, the adjusted voltage dropped precipitously while underway, but returned to normal levels as soon as we were anchored.
I have no idea why.

It's too early in the morning; that just made my head spin!

Is there a reason you had it on your last boat but not the Dragonfly?

The only zincs I have are on the shaft. I'd hate to think I'm going to find myself a day late and a dime short.

[St. Elsewhere]

Originally Posted by senormechanico

With all the talk about over and under zincing, nobody has mentioned how much voltage there should or should not be impressed on the underwater metals to be protected.

I've always noticed on my boat that with a new zinc, I get -0.7 volts on the bonding system.

An interesting side note, the adjusted voltage dropped precipitously while underway, but returned to normal levels as soon as we were anchored.
I have no idea why.

Very clever! You saved a bunch of $ over buying this one. I get a little larger negative voltage with it, and I expect that it may be due to the silver/silver chloride properties. Also, I believe that your voltage change while underway is due to the water flow creating the effect of a longer electrolyte path between your zinc and the dime electrode. The instructions that go with my unit reference a distance limit.

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[goboatingnow]

In reality this impressed current corrosion seems to be a mainly US issue. In the EU boats as a norm do not have continuous bonded underwater metals. Nor is the AC earth and DC connected. Coupled with widespread use of RCBOs it would seem to be a better code. All this and 230v floating around.

Dave

[Cheechako]

This is a long post and I havent read them all, but have you considered getting all your neighbors who are effected to sign a nice diplomatically written letter asking the offender to have a look at solving the problem as a "good neighbor"?

[senormechanico]

Originally Posted by hummingway

It's too early in the morning; that just made my head spin!

Is there a reason you had it on your last boat but not the Dragonfly?

The only zincs I have are on the shaft. I'd hate to think I'm going to find myself a day late and a dime short.

It's on the list of "to do".
I'm going to do a two color LED indicator instead of a meter.
That way, it's going to be a go/no go adjustment.

I've got the parts, just not the time right now.
Springtime for sure.

[hellosailor]

Steve, you're measuring...what? The voltage between a "silver" dime electrode and some point in your bonding system?

Wayne-
"You want X mass of zinc to protect Y mass of boat metal. " And you determine the correct mass by what? A guestimate of the amount of zinc, followed by a voltage test?

[afro]

Go change your berth
____________________
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[senormechanico]

Originally Posted by hellosailor

Steve, you're measuring...what? The voltage between a "silver" dime electrode and some point in your bonding system?

Yup.
Meter with momentary switch between bonding wire and the dime.
I mounted the dime on an insulator (nylon) so it wouldn't react with the bottom paint.

On the Dragonfly, I've got a spot where I can mount a dime, soldered to a wire on the back side and bedded in 3M5200 inside a 1" PVC plug.
It will be screwed into a PVC fitting already in place in my centerboard trunk, just below the waterline.

[sailvayu]

Originally Posted by hellosailor

Steve, you're measuring...what? The voltage between a "silver" dime electrode and some point in your bonding system?

Wayne-
"You want X mass of zinc to protect Y mass of boat metal. " And you determine the correct mass by what? A guestimate of the amount of zinc, followed by a voltage test?

Yes you are measuring the voltage flow from one metal to the other. Sort of like measuring the volt between 2 plates in a battery. This voltage is small and varies with different metals. These voltages are listed in some galvanic scales and are established norms. You want some flow from the anode to the cathode for protection but not too much. I have not heard of anyone using a silver dime but I suppose it would be close enough to work just make sure it is a pure silver dime not plated. A silver/silver chloride half cell is not that expensive (I think around 100) and is what the numbers are based on. The s/sc half cell is the neutral metal in the galvanic scale so it is used as the base of all measurements when testing.

How do you figure how much zinc? Yeah you guess based on experience. You can check by measuring voltage between the zinc and protected metals to check. This is really common sense as we have been putting zincs on boats for many years so we sort of have an idea of how much is enough. In practice when you haul your boat you should only see about 50% or less wastage from the zinc you have. If one or more of your zincs is more wasted than that you may have a problem and you should start checking things. also when you haul you should look closely at your metals, if any bronze shows a pinkish color you have a problem, stainless and aluminum are harder to tell.
Like mentioned before the problem is almost always on the boat loosing the zinc.

I think by now most can see the problem is not as simple as the OP made it out to be. you need to know how and what to test and use the right equipment. It is not rocket science but it is not as simple as putting one probe on a VOM on the rigging and the other in the water. As you can see from above all that is doing is measuring the electrical difference between the rigging and the metal in the probe, not really helpful. Having the right tools and knowing how to use them is important.

When you trow a zinc over the side with a wire attached to the boat what are you doing? Are you attaching the wire to the bonding system, the rigging, the toe rail? Is that protecting the problem area or just some other metal on the boat that does not have a problem? You have to know the problem before you can fix it. tossing a zinc over the side only makes the owner feel like he has done something. Maybe he will get lucky and attach the wire to the problem metal, and maybe not.