electrolysis, or total lack of, after 4 years

Recently pulled my boat for a bottom job after 4 years. Bottom paint was ok. Had a few barnacles, plenty of slime (mostly fresh water/mississippi river). Added 4 gallons of ablative after pressure washing. BTW, mixed 50/50 black and "clown" blue for the nicest navy blue color you could want. The most interesting thing was that my zinks were still in decent, useable condition. No evidence of corrosion on any running gear or fitting. Props were perfect. Shafts were perfect. I left the old zinks on the shafts and added new ones. The rudder zinks were fine. I have a large plate zink that is attatched electrically to the tuna tower by a flat copper strap for lightning dissapation, it was fine. I have to contribute this to my boat being totally "unbonded" by me. I have been relentless in removing all the bonding crap, and I'm paranoid about battery chargers. So far this is the least amount of electrical activity I've seen on a boat thats been in the water this long.

Zincs dont work much in fresh water. So they stay new.

There are other protection methods , magnesium .

True, freshwater makes a difference. I was just amazed at the complete absence of any kind of electrical activity.

I have to replace anodes every 2 years using magnesium in fresh water. On previous boat in fresh water never replaced anodes in 13 years that I know of probably more, I suspect they were zink.

I will change to magnesium next haulout.

Should you put both zinc and magnesium if you planning on being in both salt and fresh? I have zinc and after two years no problem when hauled out. A few barnacles on the shaft , in fresh water.

Greetings,
Mr. k. "A few barnacles on the shaft , in fresh water.". Hmm...no barnacles in fresh water as far as I know...but good question. CAN one put both zinc and mag' anodes on at once. Can't remember my electrochemistry.

RTF
I like Kulas44, I am in Louisiana about 8 miles from the Gulf. I would think with a strong and long south wind we could have a little salt water blow in.

It's more a matter of the electricity in the water where the boat is docked. As for material magnesium is better in fresh water.

Just picked up this nice explanation about zinc in fresh water off this morning's T&T digest, courtesy of "Sean":

"Can someone please explain why zinc anodes are not recommended for fresh
water."

Yes. In fresh water, the electrolyte is much weaker and the activity
level of the zinc does not support enough sloughing of the material. In
very short order, the zinc will become coated with an impermeable layer
of zinc hydroxide (the way zinc naturally oxidizes in the presence of
water, unrelated to galvanic action). Once this layer is in place, the
galvanic action will stop entirely, and the zinc essentially becomes
passive -- it provides no anodic protection whatsoever. Whatever else
on the boat is then the next least noble metal, such as an aluminum
part, then becomes the anode for the whole boat.

... The idea is to protect the prop, not to make the anode go away.

If the anode does not "go away" then it's not protecting anything.
That's how it works.

kulas44 said:

True, freshwater makes a difference. I was just amazed at the complete absence of any kind of electrical activity.

Click to expand...

It doesn't mean an absence of electrical activity. It means zinc anodes do not work in freshwater.

kartracer said:

Should you put both zinc and magnesium if you planning on being in both salt and fresh?

Click to expand...

No. Do not mix anode materials. You know, unless you like galvanic corrosion.

This thread and the info it provides is very timely. I'm hauling my boat next week and I'm going to replace my zincs, paint the bottom and straighten a prop that we used to test the water depth....("OUCH").

I do have a couple of questions. 1. Where's a place to buy zincs where they don't think they're made of solid gold? 2. When the zincs become coated with the Zinc Hydroxide and lose their effectiveness, is it possible to grind that layer off and continue to use the zincs?

I'm in fresh water and the zincs look like new except for that layer that has developed.

Thanks,

GFC

caltexflanc said:

Just picked up this nice explanation about zinc in fresh water off this morning's T&T digest, courtesy of "Sean":

"Can someone please explain why zinc anodes are not recommended for fresh
water."

Yes. In fresh water, the electrolyte is much weaker and the activity
level of the zinc does not support enough sloughing of the material. In
very short order, the zinc will become coated with an impermeable layer
of zinc hydroxide (the way zinc naturally oxidizes in the presence of
water, unrelated to galvanic action). Once this layer is in place, the
galvanic action will stop entirely, and the zinc essentially becomes
passive -- it provides no anodic protection whatsoever. Whatever else
on the boat is then the next least noble metal, such as an aluminum
part, then becomes the anode for the whole boat.

... The idea is to protect the prop, not to make the anode go away.

If the anode does not "go away" then it's not protecting anything.
That's how it works.

Click to expand...

My boat has spent a little time in salt water, probably got the barnacles then. Even given the fresh water the boat lives in it shows no electrolysis at all. In the marinas I normally inhabit I will see some indication but not this time. If the zinks were in fact not working at all (possible) I would expect to see some indications at least on the props.

Regarding the cost of zinc, zinc mines are being exhausted and no new major deposits have been in found in years while demand for zinc is rising. Get used to higher zinc prices.

Later,
Dan

Switch to aluminum anodes. They're cheaper.

I've had great success with www.boatzincs.com

Sent from my Nexus 4 using Trawler

Kulas44 When you say you unbonded everything does this also deal with grounding? You have to be careful for your boat and others boats and people in the water(fresh water in particular) that your boat while it is not losing zincs does not become a danger.

kulas44 said:

... I have to contribute this to my boat being totally "unbonded" by me. I have been relentless in removing all the bonding crap, and I'm paranoid about battery chargers. So far this is the least amount of electrical activity I've seen on a boat thats been in the water this long.

Click to expand...

If you unplug a table lamp, the light bulb will last a long time too because it does no work.

What is it about battery chargers that makes you paranoid?

What do you consider 'bonding crap'? The bonding straps are there to protect your boat's metal components. Why did you 'unbond' your boat?

Have you consulted a marine expert who advised this is the proper approach to making your zincs last longer? I'm not being sarcastic here, but seriously want to learn why you consider this the right thing to do to protect your boat from electrolysis.

Thanks

mbevins said:

I've had great success with BoatZincs.com (978-841-9978) – The Online Superstore for Zinc Anodes

Sent from my Nexus 4 using Trawler

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Its a long treatise that most wont understand or believe. Bonding is a holdover from wooden boat days and has no place on modern fg boats. Read Nigel's books. I assume that most of us here would consider him an "expert". Dont just read it, try to really understand it, study it. When you actually "know" what it says and means you will understand bonding, and why its a bad idea. BTW, his personall boat is unbonded, just like mine, with no adverse effects.

The European theory on bonding underwater metalsoften is the opposite of ours.

They believe that an unbounded bronze underwater thru hull that's totally isolated is in little danger of dezincification. P148 of Nigel Calder's second edition of Mech and Elect Manual...if interested.

I have seen plenty of examples of this and believe bonding is necessary for only some parts and certainly there needs to be a good grounding system for AC systems and bleeding off unwanted RF and lightning potential.

Bonding is totally different from grounding or lightning dissapation. The only reason there is a requirement for bonding is to prevent delignification of wood around thru hull fittings on wooden boats. PS, what parts do you think need to be bonded ? I am a proponent of no bonding of underwater fixtures at all, but, I've been wrong a couple of times this year already.

Any part that is not totally isolated from another that has dissimilar metal or the possibility of electric current or is in close proximity (say less than a couple feet) to others that do need bonding.

Shaft and prop, due to proximity the rudder...after that not much but the smart thing is to check each fitting with a silver/silver chloride electrode...

Corrosion Reference Electrode Product Specifications

Our last sailboat, a Pearson, wasn't bonded. Came that way from the factory. The surveyor noted it as a deficiency, so the insurance company wanted us to bond everything. I directed the insurance company to the chapter in Calder's book, and they removed the requirement. His analysis made total sense to me. Seven years and we never had a single problem, yet several boats with aluminum outdrives in our marina had serious issues. I chalk it up to the fact that we only had bronze and stainless in the water, so the outdrive boats acted like our zincs (which, by the way, eroded very, very slowly). Not sure if it made a difference, but I did install a galvanic isolator on that boat. Anyway, that said, our current Nordic Tug is bonded, and we have decided to keep it this way. So far, no issues, yet one of my friends in the marina just spent 20K replacing outdrives and transome plates on his boat (aluminum parts).

If your shaft is isolated from the engine with a "drive saver" type of device that is non conductive the only requirement for a sacrificial anode is due to the SS shaft and bronze or nibral prop. Even without the non conductive device (which just removes the batteries from the shaft) the protection is for the prop. If the rudder (s) are also isolated (read not bonded) they cannot influence the shaft/prop electrically. Insurance Co.s require bonding, and some still do, because wooden boats were sinking at the dock regularly due to delignification around underwater (thru hull) metal, mostly bronze alloys. This was back when dock side power was first starting to be utilized on boats. This was caused by the fact that wet wood is a semicondutor, and ferro resonant battery chargers used then were non or poorly regulated compared to better chargers today. La Marche comes to mind. The excess dc current had to go some where and the nearest and most conductive path was it. Tie everything together and give it more paths instead of just one best path. It worked, albeit kinda round about. But I am coming to grips with the fact that most folks have there minds made up and dont want to be confused with facts.

Back to the origional post, and please talk to me slooooowly as this talk of bonding and isolation has worn out the google on my device.

I move back and forth mooring 7-8 winter months in fresh and 4 - 5 summer months in the salt. What anode for me?

Thanks

Bradenvlp said:

Back to the origional post, and please talk to me slooooowly as this talk of bonding and isolation has worn out the google on my device.

I move back and forth mooring 7-8 winter months in fresh and 4 - 5 summer months in the salt. What anode for me?

Thanks

Click to expand...

IMHO, best applications regarding anodes: Salt = Zinc / Fresh = Magnesium

Caveat: I believe that zinc is OK for freshwater (many will disagree with this) as long as you dive under and scrape and wire brush scrub (bronze BBQ brush with scraper end works well) its surfaces clear of any build-up that occurs on zinc in freshwater. Scraping should happen at least in 3 month or sooner increments. From freshwater months-time you mention above... looks to me that once in mid freshwater time and at very end would suffice. More zinc surface cleanings is always better.

kulas44 said:

Even without the non conductive device (which just removes the batteries from the shaft) the protection is for the prop. If the rudder (s) are also isolated (read not bonded) they cannot influence the shaft/prop electrically. Insurance Co.s require bonding, and some still do, because wooden boats were sinking at the dock regularly due to delignification around underwater (thru hull) metal, mostly bronze alloys.

Click to expand...

My boat is un-bonded, no zinc plate from the factory. Two shaft zincs on each shaft, a zinc on each rudder and one pencil zinc in each cooler. I re-zinc every year and am running the original shafts, props and rudders. I suppose it depends on your marina and the local environment, but I believe many fiberglass boats are way over zinc'd.