Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 22-06-2007, 02:20   #31
Registered User

Join Date: Mar 2007
Location: Algarve
Boat: Coronet Elvstrom 38
Posts: 58
What is the advice, in voltage terms, for correctly anoding a bronze propeller on a SS shaft?
__________________

__________________
Idiens is offline   Reply With Quote
Old 22-06-2007, 03:27   #32
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,586
Images: 240
Underwater bronze, such as the propeller, is considered to be fully protected by the zinc on the prop shaft if the voltmeter reads between 500 and 700 mv, vs an Ag/AgCl reference.
__________________

__________________
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 20-08-2007, 04:58   #33
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,586
Images: 240
Excerpted from “The Future for Sacrificial Anodes” ~ by Bob Crundwell
Goto:http://www.jcse.org/Volume4/Preprints/V4Preprint2.pdf

The calculation of the weight of anode alloy required to protect a structure is given by a simple calculation:

W = (A x C x L) Z

Where:
W = Weight in Kg
A = Area to be protected in M2
C = Polarisation Maintenance Current Density in Amperes / M2
L = System life in Hours
Z = Anode current capacity in Ampere Hours per Kg
The individual components of this equation, with the exception of design life, are known but only approximately*.

* It is a brave designer that claims to know the true surface area of the structure. Dimensional tolerances of rolled sections of the sizes from which offshore structures are made are known quite accurately but it is surprising what bits get left out of the calculation let alone any correction for surface irregularity (one authority quoted the difference to be a factor of x2).
* Maintenance current density is variously quoted at figures between 0.140 A/M2 and 0.040 A/M2 for the same location, a factor of almost 4 times.
* Anode current capacities for Al-Zn-In alloys are variously quoted between 2550 Ahrs/Kg & 2750 Ahrs/Kg In general the lower figure is on the basis of long term field tests and the higher figure is on the basis of short term lab tests.
__________________

__________________
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
Reply

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
Autohelm - Keep or Replace? markpj23 Marine Electronics 7 16-08-2007 03:02
Aftermarket Volvo anodes seafox Construction, Maintenance & Refit 16 09-03-2007 11:58
Engine mounts - When to replace? dkall Engines and Propulsion Systems 5 13-01-2007 04:49
Sacrificial Anodes Islandmike Construction, Maintenance & Refit 5 27-11-2006 11:34
Battery charger to replace battery? lilly Electrical: Batteries, Generators & Solar 5 22-07-2006 19:11



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 07:58.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.