Reply
 
Thread Tools Display Modes
 
Old 06-09-2012, 07:30 AM   #1
Guru
 
Scary's Avatar
 
City: Walnut Grove Ca
Country: USA
Vessel Name: Cary'D Away
Vessel Model: Hatteras 48 LRC
Join Date: Apr 2012
Posts: 884
Zinc Anodes

Just replaced my Zinc' yesterday. They were still had about 75% left after two years! Boat moored in fresh water and boats in saltwater and or brackish water. What kind of life expectancy should we expect. My last boat moored in salt water and all but three months boated in salt water. Zincs every 6 months. this is my first boat to spend most of its life in fresh water. Both boats are in the 50' range. The Bayliner uses three small isolation transformers, one for each shore power line. It used a 6x12 divers zinc, all through hulls bonded to it, shaft zincs, rudder zincs, and trim tab zincs. The Hatteras uses two very large isolation transformers, shaft zincs and two rudder zincs. Two slightly different approaches, both apparently successful. what say you?
__________________
Advertisement

Scary is offline   Reply With Quote
Old 06-09-2012, 08:20 AM   #2
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
The salinity of the water, the configuration of the boat's electrical and bonding systems, and the relative "hotness" of the water in the marina introduce a lot of variables in how long zinc anodes will last.

In talking to other boaters in our marina, the zincs on most boats are ready for changing every six months or so, which is the case on ours.

Bellingham Bay has a large influx of fresh water from a fairly large river (Nisqually) and three high-volume streams (Squalicum, Whatcom, and Padden). So at many times of the year the salinity of the surface water in the marina is almost zero or actually is zero. Plus the marina is considered to be somewhat "hot."

This is why many boaters in the marina, including us, hang a zinc about ten feet underwater on a heavy cable. The other end of the cable is connected to the boat's bonding system. In our case it's clamped to one of the bronze rudder posts. The zinc-on-a-wire ensures that even when the license plate zincs aren't doing much due to poor connectivity in the layer of fresh water there is still a large zinc providing additional connectivity, and the shaft zincs last much longer. We also have shaft wipers which help extend the life of the shaft zincs.

I have heard that if one keeps a boat in fresh water alumunium anodes are preferred over zinc, but I don't know if that's really true or not.
__________________

Marin is offline   Reply With Quote
Old 06-09-2012, 08:30 AM   #3
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,920
Quote:
Originally Posted by Marin View Post
The salinity of the water, the configuration of the boat's electrical and bonding systems, and the relative "hotness" of the water in the marina introduce a lot of variables in how long zinc anodes will last.

In talking to other boaters in our marina, the zincs on most boats are ready for changing every six months or so, which is the case on ours.

Bellingham Bay has a large influx of fresh water from a fairly large river (Nisqually) and three high-volume streams (Squalicum, Whatcom, and Padden). So at many times of the year the salinity of the surface water in the marina is almost zero or actually is zero. Plus the marina is considered to be somewhat "hot."

This is why many boaters in the marina, including us, hang a zinc about ten feet underwater on a heavy cable. The other end of the cable is connected to the boat's bonding system. In our case it's clamped to one of the bronze rudder posts. The zinc-on-a-wire ensures that even when the license plate zincs aren't doing much due to poor connectivity in the layer of fresh water there is still a large zinc providing additional connectivity, and the shaft zincs last much longer. We also have shaft wipers which help extend the life of the shaft zincs.

I have heard that if one keeps a boat in fresh water alumunium anodes are preferred over zinc, but I don't know if that's really true or not.
It's the recommendation by several of the zinc companies...but even they have thier twist to the story. For aluminum outboards and outdrives...magnesium is recommended but ONLY if you stay in fresh (I think that's the idea)

Be careful about thinking you have 75% left. I was going to reuse my hull plate zincs that looked almost new.... until I hit one on the edge of a table to see if it had it's internal structure...broke in half way too easily. Probably the alloy was mostly depleted.
psneeld is online now   Reply With Quote
Old 06-09-2012, 08:33 AM   #4
Guru
 
Anode's Avatar


 
City: Missourah
Country: USA
Vessel Name: M/V Scout
Vessel Model: Sundowner Tug 30'
Join Date: Jul 2010
Posts: 645
I have used zinc on my freshwater boats for years and never had an electrolysis problem. They do get 'crusty' and need to be cleaned from time to time. Kinda of "don't mess with success" reasoning.

But.....I just re-"zinked" Scout with magnesium anodes. Why....? The swim platform is aluminum and the brackets are right at the water line. It is now bonded to the rest of boat. Only time will tell.

No way would I use mag anodes in brackish water. They wouldn't last two weeks.
__________________
Chip

Deliveries & Yacht Services
www.captainchip.com
Anode is offline   Reply With Quote
Old 06-09-2012, 08:38 AM   #5
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
One of the most popular brand of zinc anodes is Divers Dream Martyr by (I think) Canadian Metals. According to the dive service we use and our own observation, Divers Dream zincs do not go away at a linear rate. They errode at an accelerating rate. So if it took x-amount of time for 50 percent of the material to errode away, the remaining 50 percent will errode away in a lot less time.

One of the advantages of hanging a zinc down on a wire is that you get to observe what it's doing because you pull it up every time you take the boat out and you can pull it up to check it as often as you like. So we look at ours almost every weekend. And the errosion rate is indeed an accelerating curve, if you will.

It may be that all zinc anodes behave this way. But our dive shop referenced this accelerating errosion specifically to the Divers Dream anodes. They're very good zincs and are what the shop uses, but they did want us to kmow they have this characteristic.
Marin is offline   Reply With Quote
Old 06-09-2012, 10:07 AM   #6
Guru
 
Anode's Avatar


 
City: Missourah
Country: USA
Vessel Name: M/V Scout
Vessel Model: Sundowner Tug 30'
Join Date: Jul 2010
Posts: 645
I got my mag anodes from Canada Metals. Magnesium is so much lighter than the old zincs is just didn't feel right putting them on.

They make the Divers Dream in magnesium and that went on the stern. I fab'd a stainless bracket for it. Will try to get some pictures of it today.

I bought a tear drop anode for my stern bearing housing which is isolated from the rest of the bonded system by the cutlass bearing. Put a shaft anode as I have just enough clearance to get on it (w/o impeding water flow). Replaced the old rudder anode with the Diver's Dream on the stern for easy access and observation.
Interesting note: All the the mag anodes had "Canada Metals" and "Martyr" in the casting. On the back was a tiny paper sticker...."Made in China". School is still out.
__________________
Chip

Deliveries & Yacht Services
www.captainchip.com
Anode is offline   Reply With Quote
Old 06-09-2012, 10:33 AM   #7
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
Yes, Canadian Metals has a lot of their stuff made in China these days (including Rocna anchors). Don't know that this reflects on the quality of the product. Depends on the oversight of the parent company I suspect. It certainly has an effect on the price you pay.

Don't know about the plants Canadian Metals uses, but China has some of the most advanced magnesium manufacturing facilities in the world.

I'm in China now and when you see what's happening in manufacturing over here it's hard to imagine there is still anything on the planet these days that isn't made in China.
Marin is offline   Reply With Quote
Old 06-09-2012, 08:48 PM   #8
Guru
 
Scary's Avatar
 
City: Walnut Grove Ca
Country: USA
Vessel Name: Cary'D Away
Vessel Model: Hatteras 48 LRC
Join Date: Apr 2012
Posts: 884
Hardly a dim light bulb hanging off a wire like many think!!

Quote:
Originally Posted by Marin View Post
Yes, Canadian Metals has a lot of their stuff made in China these days (including Rocna anchors). Don't know that this reflects on the quality of the product. Depends on the oversight of the parent company I suspect. It certainly has an effect on the price you pay.

Don't know about the plants Canadian Metals uses, but China has some of the most advanced magnesium manufacturing facilities in the world.

I'm in China now and when you see what's happening in manufacturing over here it's hard to imagine there is still anything on the planet these days that isn't made in China.
That's the problem in the US, many of our companies are stuck with old technology when the Chinese are using the latest and best.
Scary is offline   Reply With Quote
Old 06-09-2012, 08:57 PM   #9
Guru
 
Scary's Avatar
 
City: Walnut Grove Ca
Country: USA
Vessel Name: Cary'D Away
Vessel Model: Hatteras 48 LRC
Join Date: Apr 2012
Posts: 884
West Marine

West Marine sells both mag and zinc in the Cal Delta. Perhaps my using the zinc in fresh water is the reason they last so long. I seem to be having no problem with electrolysis but maybe using Mag would provide better protection. I'm running original props and shafts and have the new factory spares that came with the boat. The boat has spent most of it's life in fresh water with the exceptions of cruising time. When we did the survey we looked hard at the props and rudders for zinc depletion and they looked good. Is this a science or art? Maybe luck? I'm using Canadian Metals and the new ones sold by West had China on them as well.
Scary is offline   Reply With Quote
Old 06-13-2012, 02:20 PM   #10
Senior Member
 
fstbttms's Avatar
 
City: Under a boat, in a marina in the San Francisco Bay
Country: USA
Join Date: Mar 2012
Posts: 447
Here is my $.02, based on my 18 years a professional hull cleaner:

1.- Zinc anodes should only be used in saltwater
2.- Canada Metal's Chines-made "Martyr" brand zincs are inferior to either Canadian-made Reliance brand or American-made Sea Shield brand zincs
3.- I have never found "Divers Dream" plate zincs (made by all the major manufacturers) to deplete in any particular fashion. If yours depletes faster after a certain percentage is gone, that is probably specific to your boat
__________________
Clean bottoms are FastBottoms!
fstbttms is offline   Reply With Quote
Old 06-14-2012, 01:47 AM   #11
Art
Guru
 
Art's Avatar
 
City: SF Bay Area
Country: USA
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 7,983
My experience tells me that zinc works great in salt water with no maintenance needed, except to change it when new zinc is required. Iíve found that zinc can also work very well in fresh water too, and last a looong time compared using Zinc to salt water... in fresh water zinc only protects well AS LONG AS... in fresh water, you diligently swim under boat and vigorously SCRAPE/SCRUB ZINC SURFACES CLEAN, every 3 to 4 months. Otherwise, if you donít keep the Zinc surfaces clean from the coating that occurs in fresh water the zincí abilities are greatly diminished, eventually negated. If you donít want to keep zinc surfaces clean then Mag anodes are a good bet!
__________________

Art is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 07:47 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012