Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 24-01-2010, 04:22   #1
Registered User

Join Date: Jun 2008
Posts: 128
The Life of Zinc

Howdy folks:
Just got around to replacing zinc anodes (+ 1 aluminum anode) on my steel hulled 42-footer. I am tied to a dock in a salt water commercial harbor. Four months on the high seas and the zincs were on for 8 months. They were down to 10% left.
I have also added a couple of hunks of zinc over the side hanging by copper wire while I stay here for the next couple of months.
What is normal life for zincs on a glass boat and or steel boat?
Thanks for any info/ advice.

rigormortis is offline   Reply With Quote
Old 24-01-2010, 04:33   #2
Registered User
markpj23's Avatar

Join Date: Nov 2005
Location: Black Hills, SD
Boat: Now Boatless
Posts: 1,148
Images: 47
It really depends upon the boat AND the environment (stray currents) where you are. I had a shaft zinc on for 14 months and it was only 50% wasted... on a boat with an isolation transformer and zero metal below the waterline except for shafting. Also in a marina with a good electrical system.

Your experience at 8 months is a clue. If you have another at-sea interval try to measure that for the "best" life you can expect from your zincs.


markpj23 is offline   Reply With Quote
Old 24-01-2010, 05:07   #3
Moderator Emeritus
GordMay's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 29,347
Images: 240
Where you at, Pete?

Even though Zinc & Aluminum are very close on the galvanic series, I generally wouldn’t mix anode types, as the less noble Zinc (anodic) may corrode to protect the more noble Aluminum (cathodic) metal.

This has likely been happening, if you find the Zinc anodes eroding more quickly than the Aluminum.

Pure zinc has a theoretical capacity of 372 Ampere Hours per pound. That means at 1 amp,it would take 372 Hours to consume a pound of zinc. Now,zinc operates at about 95% efficiency so it would actually be approx.
353 AmpHrs.

On a steel hull, the current requirements for protection (to about -800 to -1050 mv) could be between .3 ma (milliamp) and 6 ma. per sq. ft. for submerged protection, depending on coating quality or lack thereof and very little water flow.

So, for example, a 25lbs zinc anode, putting out 2 amps would last approx. (25lbs x 353 amphrs/ 2 amps/24hrs) or
8825/2= 4412.5/24= 183.8 days.
Keep in mind that this is all theoretical and has many variables

Anodes should be replaced at about 50% erosion.
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

GordMay is offline   Reply With Quote
Old 24-01-2010, 06:08   #4
Registered User
fishwife's Avatar

Join Date: Aug 2009
Location: South coast of England, moving around a bit.
Boat: Long range motor cruiser
Posts: 750
Slightly off topic (sorry). What do you do with the removed anode? Does anyone know a way of recycling them?

The message is the journey, we are sure the answer lies in the destination. But in reality, there is no station, no place to arrive at once and for all. The joy of life is the trip, and the station is a dream that constantly out distances us”. Robert Hastings, The Station
fishwife is offline   Reply With Quote
Old 24-01-2010, 12:43   #5
Registered User

Join Date: Jun 2008
Posts: 128
I am in Iquique, northern Chile. It is mainly an industrial port with a good-sized anchovy fishery as well as inshore fishermen. I am here for the paragliding which is great (no rain, ever). Took 4 months to get here from Portland, OR. It's a shitty sail/motor from Ecuador down but I knew that. From here I will head to Easter Island/Pitcairn and west.
I will digest your answer to my query (thank you) with a dictionary, a pile of Nigel Calder books and maybe a digimeter by my side.
rigormortis is offline   Reply With Quote
Old 24-01-2010, 15:08   #6
Marine Service Provider
fstbttms's Avatar

Cruisers Forum Supporter

Join Date: Oct 2006
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 3,267
Originally Posted by fishwife View Post
Slightly off topic (sorry). What do you do with the removed anode? Does anyone know a way of recycling them?

I have recycled hundreds of pounds at a local scrap metal dealer. If you have just a small amount, not sure what you can do with it. Find a recycle bin on the street domewhere maybe?
fstbttms is online now   Reply With Quote
Old 24-01-2010, 15:44   #7
Registered User
clsailor's Avatar

Join Date: Apr 2007
Location: Middle Chesapeake Bay
Boat: Cheoy Lee Clipper 36 - Rapport
Posts: 95
Images: 5
Thumbs up

Pete, I am at a marina that is about four years old in the middle Chesapeake Bay. I have a isolation transformer and my diver has not replaced my zinc in two years. Fiberglass hull.

"I got some place I gotta be, but I don't know where it is"
John Borland (1949-1994)
clsailor is offline   Reply With Quote

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Land Life / Boat Life Ocean Girl Families, Kids and Pets Afloat 59 14-06-2010 02:04
Life Vests or Life Jackets sbenest Health, Safety & Related Gear 11 23-12-2009 10:05
Zinc Fish unbusted67 Electrical: Batteries, Generators & Solar 16 13-08-2009 10:04
Zinc Question Charlie Construction, Maintenance & Refit 8 15-10-2008 12:54

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 07:17.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.