No AC hook-up why galvanic crrosion? - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #1  
Old 02-11-2011
Bradhamlet's Avatar
Senior Member
 
Join Date: Nov 2002
Location: Simi Valley CA
Posts: 152
Thanks: 2
Thanked 3 Times in 3 Posts
Rep Power: 12
Bradhamlet is on a distinguished road
Unhappy No AC hook-up why galvanic crrosion?

Hey why and how do I stop the prop pitting on my boat that is not hooked up to the dock's AC current? The boat is only DC, there is a shaft zinc and strut zinc which I change often (every 6 months). The boat yard tells me it is my neighbors boat, but this has happened at different marinas for the past 10 years. I am becoming frustrated, any ideas?
Brad
Lancer 36 1981
Channel Islands CA
Reply With Quote Share with Facebook
  #2  
Old 02-11-2011
Fstbttms's Avatar
I don't discuss my member
 
Join Date: Feb 2003
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 2,034
Thanks: 2
Thanked 18 Times in 18 Posts
Rep Power: 12
Fstbttms is on a distinguished road
Do you leave your battery switch on?
Reply With Quote Share with Facebook
  #3  
Old 02-11-2011
Bradhamlet's Avatar
Senior Member
 
Join Date: Nov 2002
Location: Simi Valley CA
Posts: 152
Thanks: 2
Thanked 3 Times in 3 Posts
Rep Power: 12
Bradhamlet is on a distinguished road
Yes I do leave the power on? Is that the answer? I noticed a few of your posts and respect your profession and opinions.
Brad
Reply With Quote Share with Facebook
  #4  
Old 02-11-2011
Fstbttms's Avatar
I don't discuss my member
 
Join Date: Feb 2003
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 2,034
Thanks: 2
Thanked 18 Times in 18 Posts
Rep Power: 12
Fstbttms is on a distinguished road
Well, I'm no electrical expert, but 12 volts bleeding into a wet bilge can be a problem. You may have a bare wire somewhere in the 12-volt system. I'd start looking there.
Reply With Quote Share with Facebook
  #5  
Old 02-11-2011
kd3pc's Avatar
Senior Member
 
Join Date: Oct 2006
Location: Callao, VA
Posts: 1,311
Thanks: 0
Thanked 8 Times in 8 Posts
Rep Power: 8
kd3pc is on a distinguished road
you have a potential difference between your boat/systems and the marina, somewhere.

You can get a decent digital multimeter and test things, or have a marine electrician with one hour show you where things are leaking.
Reply With Quote Share with Facebook
  #6  
Old 02-11-2011
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 9 Times in 9 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
I wrote a post on testing for a DC side leak a while back. Here it is...

Quote:
If you want to test to see if you have a DC-based ground leak, the test for that is rather simple. The steps for seeing if you have a DC-ground leak are as follows:

First—the preliminary diagnosis test:


1) Turn off all equipment and disconnect any solar panels
2) Disconnect the positive side of the battery banks.
3) Leave the main battery isolation switch turned on for the bank in question
4) Set the meter to VDC mode, range appropriate for your battery bank
5) Connect the meter between the positive terminal and the disconnected cable

The meter should give no reading. If it reads XX volts for your XX VDC system, one of two things is happening.

1) You've left some equipment connected and turned on. This could be a bilge pump, a power feed to a stereo for the radio's memory and clock functions, or a hard-wired fume detector.

2) If you've disconnected all the "hard-wired" equipment and still get a reading, then you've most likely got a ground leak in your boat's DC system.

The Ground Leak Check:

1) Set the meter in Ohm mode and set it to the lowest range (x1).
2) Connect the leads of the Ohm-meter (or multimeter in Ohm mode) to the disconnected positive lead and the negative terminal of the battery.

The meter is now reading the resistance of any circuit to ground that exists in the boat's wiring. The reading on the Ohm meter display can help you identify the cause of the leak.

0-10 Ohms means it is most likely a piece of equipment left on
10-1k Ohms is a low-drain piece of equipment left on, or a serious ground leak
1k-10k Ohms is a minor leak
10k+ Ohms is an insignificant leak

How Big is The Leak?

The ammeter function of the multi-meter can tell you what the current leakage is. If your meter can read up to 10 Amps DC, then you can use it to measure amperage for leaks down to about 1.3 Ohms resistance on a 12 VDC system, or 2.6 Ohms for a 24 VDC system.

To see how big the leak is, put the probes on the positive battery post and the disconnected cable. The meter readings can be interpreted as shown:

<1mA — insignificant leakage
1–10mA — minor leakage
10mA–1A — major leak or some equipment left on
>1A — Usually some equipment left on.
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Share with Facebook
  #7  
Old 02-11-2011
Senior Member
 
Join Date: Sep 2006
Location: Texas
Posts: 526
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
CapnBilll is on a distinguished road
What sailing dog said. The zincs act as a sacrifical anode making the rest of the boat more cathodic, (negative), but the voltage is low <1volt. a 12v battery wire in the bilge blows it right out. Since most electrical devices will be grounded to the boats ground, any could be leaking, (wet, corroded, worn insulation, etc...). Bilge pump wires are a good suspect.
__________________
The Sun has Risen on a New Day filled with the Promise of Adventure.
Reply With Quote Share with Facebook
  #8  
Old 02-11-2011
Fstbttms's Avatar
I don't discuss my member
 
Join Date: Feb 2003
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 2,034
Thanks: 2
Thanked 18 Times in 18 Posts
Rep Power: 12
Fstbttms is on a distinguished road
Quote:
Originally Posted by CapnBilll View Post
Bilge pump wires are a good suspect.
Just a month or so with a bad bilge pump wire:


Reply With Quote Share with Facebook
  #9  
Old 02-11-2011
Bradhamlet's Avatar
Senior Member
 
Join Date: Nov 2002
Location: Simi Valley CA
Posts: 152
Thanks: 2
Thanked 3 Times in 3 Posts
Rep Power: 12
Bradhamlet is on a distinguished road
Thanks sailingdog and fastbottom for the info. I will be looking into it this weekend. It was helpful for the range of leakage. And I don't want my prop ever looking like that one!
Brad
Reply With Quote Share with Facebook
  #10  
Old 02-11-2011
JKCatalina310's Avatar
Senior Member
 
Join Date: Nov 2010
Location: Randolph, MA
Posts: 164
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 4
JKCatalina310 is on a distinguished road
What type of water?

There are 3 different types of anodes: zinc, magnesium and aluminum.

Depending on the type of water you are in, you should be using a specific type of anode. Zinc is for salt water; magnesium is for brackish; and aluminum is for fresh water.

Also, there is a good article in this months Cruising World.
__________________
“Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.” -Mark Twain
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
galvanic corrosion ezbreezes1 Caliber 2 05-11-2010 08:37 PM
Galvanic corrorsion? saltypat Gear & Maintenance 4 08-08-2007 11:23 PM
Galvanic Isolators Gulfislander Gear & Maintenance 1 06-11-2007 05:38 PM
Galvanic Corrosion Duke 7184 Gear & Maintenance 11 03-17-2007 09:09 AM
Galvanic Isolators Tom Wood Gear and Maintenance Articles 0 08-06-2002 08:00 PM


All times are GMT -4. The time now is 11:02 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012