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Old 29-09-2014, 03:09   #1
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How to Measure Galvanic Issues

I've tried the search function and can't find it. Seems to me I saw a post a while back about how to measure if your boat has galvanic issues.

Mine seems to burn through zincs pretty fast and I'd like to see if it has issues.

The post told how to measure using a normal electical volt/amp/ohm meter.

Anbody got an answer?

Thanks

Carsten
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Old 29-09-2014, 03:25   #2
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Re: How to Measure Galvanic Issues

Electrolysis 101 | YachtPals.com
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Old 29-09-2014, 10:03   #3
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Re: How to Measure Galvanic Issues

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OMG, I thought that forum had expired years ago. I better go take a look and answer some questions.
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Old 29-09-2014, 17:06   #4
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Re: How to Measure Galvanic Issues

I just purchased some zincs and noticed the vendor also sells a silver/silver-chloride (Ag/AgCl) reference electrode with user's guide for performing corrosion potential surveys on boats. It's not cheap, $125.

Here's the link but I have no idea how useful it actually is.

Corrosion Reference Electrode Product Specifications
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Old 29-09-2014, 17:26   #5
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Re: How to Measure Galvanic Issues

My dad's alaskan has a built in system. He keeps track of what's normal. Every time he gets an insurance survey it gets written up as Inop. Duh! The boat is out of the water! Galvanic action = zero.
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Old 29-09-2014, 17:34   #6
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Re: How to Measure Galvanic Issues

Silver chloride anode is easy to use. You just need a voltmeter one side connected to the hull, the other to the anode . You just hang the anode over the side at different places around the boat and measure the voltage generated. Then consult a table which will tell you whether your anodes are doing their job. It should come with a full set of instructions.

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Old 29-09-2014, 18:13   #7
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Re: How to Measure Galvanic Issues

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Never trust any information from anyone who uses the term "electrolysis". Use of that term shows an incomplete knowledge of the processes involved.
Electrolysis refers to the chemical changes in the electrolyte due to the passage of electrical current, it does NOT refer to the corrosion process which is either a "galvanic" or "stray" current issue. An standard multimeter will not tell you what you need to know. The silver, silver chloride cell is the way to go. as stated by the another poster.

The built in system referred to by yet another poster is a Capac system and these work quite well (when in water )
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Old 29-09-2014, 19:54   #8
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Re: How to Measure Galvanic Issues

I used a CAPAC system but it is a PITA. I wondered why the previous owner had disconnected it so I tried it for a year and abandoned it too.

Firstly it uses 12 volt power so unless you are a cocktail boat, keeping batteries up becomes a problem. Second, it concentrates the protection at a limited number of electrodes that attempt to cover the whole hull. With enough voltage to get the correct level of protection as measured by the control cell location, the areas around the electrodes becomes over protected. The DC current in this area causes ELECTROLYSIS in the seawater forming Chlorine gas bubbles which will eat the antifouling paint off the adjacent hull and bleach color out in streaks rising to the surface.
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Old 29-09-2014, 20:03   #9
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Re: How to Measure Galvanic Issues

I'm not sure why you would use the Silver Chloride Cell. Presumably you could go around the hull at varying distances and make a contour map of voltage measurements. Unfortunately there is no way to tell if the voltages are caused by your boat or other boats and fixtures in the vicinity.

From that you can deduce that you have a galvanic problem, DUH you knew that already. It might show you areas of very high concentrations that you "might" be able to attribute to an adjacent boat or dock but you still have a galvanic problem despite knowing the origin. There is hardly any way a zinc will not work and diving on it to inspect will tell a lot more than a table of voltages.

Better to spend the $125 on a Galvanic Isolator and some zincs and work on protection rather than diagnosis.
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Old 30-09-2014, 11:38   #10
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Re: How to Measure Galvanic Issues

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Originally Posted by carstenb View Post
I've tried the search function and can't find it. Seems to me I saw a post a while back about how to measure if your boat has galvanic issues.

Mine seems to burn through zincs pretty fast and I'd like to see if it has issues.

The post told how to measure using a normal electical volt/amp/ohm meter.

Anbody got an answer?

Thanks

Carsten
I may sound like a simpleton? Have you checked your shore power as a contributor? I believe a floating ground can contribute to eating zincs.

Give may best to the Little Mermaid.
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Old 30-09-2014, 12:22   #11
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Re: How to Measure Galvanic Issues

you need a sliver silver chloride half cell and an electric meter that measures in milliamps
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