Zincs

I am new to Trawler forum. We have purchased a Jefferson 53 And I have recently had a diver install 16 new zincs. And some of my friends have indicated that that’s a lot zincs. My boat broker suggested that I use or consider aluminum instead of zincs. Our boat is in saltwater and we plan to keep it there indefinitely. I have ordered a new set of sinks from boatsinks.com and I find that the price is 1/2 of what the diver charged me. Also the diver would like me to set up a maintenance program with him. The diver charged me $300 to install the zincs and do a partial cleaning of the boat. That seem like a reasonable charge for the diver. Any thoughts on the above regarding divers and zincs would be appreciated.

I used to buy my own zincs and have the diver install them. He would change a small fee to install them. But it was better than paying his price for the zincs. He has to make a living and stocking the zincs does cost. I don’t remember what he charged for the install but it worked out cheaper.

When I kept my boat in the water and had the bottom cleaned every other month, I would keep 1 or 2 of each zinc type on the transom. When the diver came to clean, he would change the bad zincs at no extra charge using the ones I provided.

As I recall, he changed the prop shaft zincs mostly, never the trim tab zincs and maybe every year or so for the transom zincs. For this single engine boat, I had one prop shaft zinc, two trim tab ones and two transom zincs for a total of five. Sixteen sounds crazy.

David

Yo Monti - Welcome!

I guess your boat is kept in 100% saltwater??

IMO... too many zinc is better than too little. Please tell us where you find places for "16" new zincs... does seem like an awful lot.

To many annodes can cause more problems than they solve, especially on timber.

Our boat is 3' shorter, only one engine, and has a grand total of three (3) zincs. One on the rudder, one on the swim step support, and one on the transom. Prop is CPP, so no place to hang zinc, but shaft is bonded to rest of boat bonding system.

I to am curious where the diver found places to attach 16 zincs?!? If twin screw, I can see maybe MAYBE eight . . . but SIXTEEN?!?

Jefferson 53 has 14 zincs. 4 in the rudders, 2 on the transom, 4 on the two shafts, 2 on the trim tabs and 2 on the bow thruster.
My diver was mistaken…still that is a lot of zincs!

That sounds about right. Don't forget the anodes in the engine(s) and generator heat exchangers and transmission coolers if so equipped. Zinc is best for saltwater; aluminum for brackish but good for saltwater and freshwater; magnesium is best for freshwater.

Support your local bottom cleaner. Timely cleanings and anode replacements will pay for themselves in bottom paint longevity and repairs from missing anodes.

Ted

I assume divers use add on’s to the price of their services. I have no problem with that if it’s part of the industry’s practice. Still learning…

In the relative scheme of things, anodes are a minimal cost. If you're not hauling annually, let the diver supply them. I never want to be thought of as a PIA customer when I need the diver ASAP.

My preference and what many consider the best zincs are Camp.

Ted

I would consider an Evergard or similar system to eliminate all of those zincs and have just two "plate zincs" on the transom. I have had the Evergard system on my trawler for 22 years and can't complain.

Simi 60 said:

To many annodes can cause more problems than they solve, especially on timber.

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Yup - On timber! Far as I know... not on fiberglass.

a proper survey of the underwater metals using a meter and a half cell is the best way to see if you're in the zone as far as anodes are concerned.
it is definitely possible to over or under protect any boat that has power systems.
i typically let the diver supply the zincs. the exception would be anything out of the ordinary. the thruster zinc is drilled specifically for it's mountings, so i supply that one. i keep every zinc the boat uses in my spares in case he doesn't have them on hand as well.

Art said:

Yo Monti - Welcome!

I guess your boat is kept in 100% saltwater??

IMO... too many zinc is better than too little. Please tell us where you find places for "16" new zincs... does seem like an awful lot.

Click to expand...

Still do not understand 16 zinc locations on a boat your size... can you list them for me/us?

I have 9 under hull anodes in following locations... some say 4 too many; i.e., only need one each shaft and none on stainless trim tabs. But, like I mentioned in my quote above. "IMO... too many zinc is better than too little."

- Two on each shaft
- one on each rudder
- one on each trim tab
- A "drivers dream" center on transom

The Mediterranean is one of the saltiest seas but we only use one lead on the shaft and 2 on the rudder, all the seacocks are bonded and we only lift out once every 5 years.
Aluminium will disappear very quickly in salt water and normally only used in fresh.

Keep in mind, this was a first time change. Most of those will seldom need replacement. Sounds like your diver was reasonable and thorough.

As to the price of anodes, they also vary in quality, but the problem is your diver is likely paying more locally than boatzincs sells them for. He's likely then only getting about a 20% discount from a high retail price. So, he is not profiting as much as you may believe.

We prefer to keep our own anodes in inventory, not to save money, but to always be sure we've got the exact one we want, full OEM. Then we're willing to pay generously for inspection and replacement. You likely paid less for replacing them since your diver got a profit on selling them to you.

I would let the convenience and quality be the determining factors and not worry about what are ultimately minor cost differences. Having a quality diver is extremely valuable.

And then even with the best of divers, I would have a camera of some sort (Go Pro works fine) and regularly examine before and after. Not secretively, but even with him if you're there at the same time, just taking care in the bot bottom, and keeping an eye on bottom paint and underwater gear.

Now we get lots of bottom cleaning and none of ours involves any scraping. If they have to scrape, you're not doing it often enough. Scrapers are not even allowed on site. Only soft materials. Our yard is amazed at the time we get from our bottom paint.

I have five. Two prop shafts, one transom, one on each rudder. 14 sure sounds like a lot to me, and I've always been taught more is not always better.

kthoennes said:

I have five. Two prop shafts, one transom, one on each rudder. 14 sure sounds like a lot to me, and I've always been taught more is not always better.

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OP - Says... "I have recently had a diver install 16 new zincs."

Let's conjecture

2 on each of 2 shafts = 4 [actually, only one on each shaft if okay]
1 on each of 2 rudders = 6 total
1 each on each trim tab = 8 total [actually, stainless tabs need none]
1 on each of a bow and stern thruster = 10 total

Sooo - where are the other 6 anodes placed?? Did the diver count correctly regarding anodes replaced - just wondering??!!

Sacrificial anodes

I am an experienced and certified corrosion technician. There are three types of material used for sacrificial anodes in the marine industry: zinc, aluminum and magnesium.

The traditional zinc anode can only be used in salt water; aluminum anodes can be used in salt or brackish water and magnesium anodes can only be used in fresh water.

On the West Coast of Florida, I recommend that my clients switch from zinc to aluminum anodes for the following reasons:
1. Pound for pound they produce 50% more amp-hours than zinc. Therefore; an equally sized aluminum anode will last about 50% longer.
2. Aluminum anodes produce about 0.050mVDC more potential measured against a standard reference anode. Since the potentials we deal with in the galvanic series are very small, any increase in protective potential is usually good.
3. Zinc anodes include cadmium in the manufacturing process. Cd is a heavy metal that stays present as the anode corrodes, sinks to the bottom, and then works its way up the food chain. Heavy metals are not good for humans to ingest.
4. Aluminum anodes cost about the same or are slightly less expensive than zinc anodes of the same size and are available at my local West Marine.

The above are general comments. Fiberglass, aluminum, steel and wood boats all have cathodic protection requirements unique to the basic hull material. Aluminum underwater components, e.g.; sail drives, Volvo IPS drives and Zeus pod drives all have unique cathodic protection requirements.

Finally, the diver that performs your hull husbandry is the first line of defense against corrosion issues and is the early warning system for the onset of the sometimes extremely destructive stray current corrosion. Heed the advice of a competent diver.

Charlie... good to hear from an expert.

Can you tell me... is it basically ok to use zinc in "non hot" areas of freshwater as long as you monthly [or there abouts in your service schedule] fully scrape clean all the gathering oxidation that forms on zinc's surface in fresh water?

In other words, as long as zinc's surface is kept clean doesn't zinc still perform as an anode in freshwater?

Thanks in advance for your reply. - Art

Art #20:
Zinc has a potential against a Ag/AgCl reference sell of about 1000mVDC in seawater. Magnesium anodes have a potential of about 1600mVDC in seawater. That 600mVDC is a huge difference in the cathodic protection world.

As freshwater is not nearly as conductive as saltwater, the potential provided by the Mg anodes is required to provide enough protective current to shift the potential of the protected metal (cathode) more negative.

Galvanic corrosion ceases in seawater when the cathode potential is shifted more than 200mVDC negative. There is an ongoing study to determine what the Goldilocks shift in potential should be in freshwater.

Cleaning the deposits off the zinc anodes cannot hurt.

CharlieJ said:

Art #20:
Zinc has a potential against a Ag/AgCl reference sell of about 1000mVDC in seawater. Magnesium anodes have a potential of about 1600mVDC in seawater. That 600mVDC is a huge difference in the cathodic protection world.

As freshwater is not nearly as conductive as saltwater, the potential provided by the Mg anodes is required to provide enough protective current to shift the potential of the protected metal (cathode) more negative.

Galvanic corrosion ceases in seawater when the cathode potential is shifted more than 200mVDC negative. There is an ongoing study to determine what the Goldilocks shift in potential should be in freshwater.

Cleaning the deposits off the zinc anodes cannot hurt.

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"Galvanic corrosion ceases in seawater when the cathode potential is shifted more than 200mVDC negative. There is an ongoing study to determine what the Goldilocks shift in potential should be in freshwater."

Please post results of that study as they come to light. I do all my own bottom maintenance; it's one of my joys in boat ownership. Found that regularly cleaning the surface [scrub the anodes clean with a BBQ bronze brush and scraper] works well for continued zinc anode action in 100% fresh water. But, if left unattended the zinc will accumulate too much surface coating to continue to work well.

Cheers!

Art -

Art,

Why would you want to add to the ongoing maintenance of your boat? Why not just use aluminum anodes and be done with it until they need replacement? Besides aluminum anodes are better for the environment.

Comodave said:

Art,

Why would you want to add to the ongoing maintenance of your boat? Why not just use aluminum anodes and be done with it until they need replacement? Besides aluminum anodes are better for the environment.

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Well, Dave... Not to get too kinky... This is an important part of my hands-on boat porn.
LOL

I simply love to often pat all sections of my boat's bottom! Rub my hands on her slick shafts. Check all anodes carefully. Feel the razor sharp edges of her clean blades. Pull on her rudders to experience bearing condition, tug at her cutlass regions and clean-out her raw water intake grates. I do all my under boat maintenance with just mask, fins and appropriate hand tools. Having been brought up doing mid-depth free diving I've been lucky enough to weeks from turning 70 still have continued good breath control.

While not aboard I also do extensive breath exercises in my weight lifter gym, that's right next to my office.

Pretty much the way I feel about it... If I can't swim under my boat to care for her needs then I probably shouldn't be boating any longer. Different strokes fer different folks!

I can understand all of that except using zinc instead of aluminum. Maybe think about the heavy metals that are getting into the water when you scrape on the zincs.

Comodave said:

I can understand all of that except using zinc instead of aluminum. Maybe think about the heavy metals that are getting into the water when you scrape on the zincs.

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Rest your mind! I changed to mag a few years ago and went to aluminum at haul last fall. Zinc is in my past!!

That is the best plan.

Comodave said:

I can understand all of that except using zinc instead of aluminum. Maybe think about the heavy metals that are getting into the water when you scrape on the zincs.

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Like many cases, our first coastal boats came with zinc anodes. It was ok, as they never ventured into true fresh water but did see brackish. Then we were enlightened in 2014. Boat built in Washington, mainly ocean going vessel, all aluminum anodes by builder. Why? Lake Washington. Columbia River. Even the inland passage. In fact, Elliott Bay measures at the upper end of brackish. All the Estuaries on inland to Alaska. Closer to home, much of Chesapeake is Brackish. Potomac is fresh. Delaware goes from salt to fresh. We changed everything from that time to present to aluminum anodes. Simple and works for all. In Europe, what about the Thames and Seine and inland waters of the Netherlands?

Then the ultimate anode challenge, the Great Loop. We ran into boaters who were changing back and forth, talking about what a pain it was. We just stuck to aluminum. Now, we do not have any pods or aluminum drives that would interfere. With watermakers, we're more aware of salinity and I suspect very few people here boat only in one type water. Boatzincs has two sets of charts covering all waters. Not one situation in which Aluminum isn't acceptable. Boat life is complicated enough without worrying if you have the right anodes, if you need to change, if your anode is damaging the sea, so once again we refer to the strategy of KISS.

If you are 100% certain you only boat in salt or fresh then perhaps zinc or magnesium is your choice. Just remember when you decide to cruise elsewhere and even 100% salt, I'd still choose aluminum. Aluminum also has the benefit of outlasting both zinc and magnesium.

Our diver had a customer who insisted on zinc and was constantly having problems although claiming he only boated on the two coasts, about half the time on the Atlantic and half on the Gulf. However, it turns out he crossed back and forth through the Okeechobee several times a year and even spent a few days fishing the Okeechobee on some of the crossings. Okeechobee is fresh water. Switched to aluminum and no more problems.

And here is one for you. What boat material should never use Magnesium anodes even on fresh water? Wood.

monti said:

I am new to Trawler forum. We have purchased a Jefferson 53 And I have recently had a diver install 16 new zincs. And some of my friends have indicated that that’s a lot zincs. My boat broker suggested that I use or consider aluminum instead of zincs. Our boat is in saltwater and we plan to keep it there indefinitely. I have ordered a new set of sinks from boatsinks.com and I find that the price is 1/2 of what the diver charged me. Also the diver would like me to set up a maintenance program with him. The diver charged me $300 to install the zincs and do a partial cleaning of the boat. That seem like a reasonable charge for the diver. Any thoughts on the above regarding divers and zincs would be appreciated.

Click to expand...

Many have asked are you "over zinc-ed"?
The best way to tell if you are handy with a meter is to buy the Corrosion Reference Electrode from BoatZinc.com
https://www.boatzincs.com/corrosion-reference-electrode.html. The tool comes with instructions and is easy to use. Plus if you have technical questions the owner is easy to talk to and very knowledgeable.


And as several have said aluminum is better protection and better for the environment.

Regarding the # of zincs, he may be counting a pancake style zinc, like you would use on a rudder or trim tab, as 2 zincs. So he may in fact have 14 or 16 pieces of zinc but not 14-16 locations for zincs. Also seems like AL makes more sense than Zinc these days especially for those of you who don't haul your boats seasonally and have them replaced by divers. My understanding is you will get longer life from AL but I haven't switched to them yet. I know that when my boat is hauled after a 6 month season in mostly salt water, my zincs are pretty well worn and in need of replacement each spring.