Why not mix anodes types? - 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 > General Interest Forums > Gear & Maintenance
 Not a Member? 
  #1  
Old 10-15-2010
zAr zAr is offline
Senior Member
 
Join Date: Feb 2009
Posts: 136
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 6
zAr is on a distinguished road
Why not mix anodes types?

Why should we not mix anodes, for example putting both a zinc and a magnesium on the prop shaft of a fiberglass boat in freshwater?

Follow up question: How can you tell which type is being used? As for example when the previous owner doesn't know these sorts of things and the old anode is difficult to get off and the yard says to let it dissolve on its own and you want to add another anode.
__________________
RS

Last edited by zAr; 10-15-2010 at 01:43 PM.
Reply With Quote Share with Facebook
  #2  
Old 10-15-2010
RichH's Avatar
Senior Member
 
Join Date: Jul 2000
Location: Pennsylvania
Posts: 2,584
Thanks: 9
Thanked 40 Times in 36 Posts
Rep Power: 14
RichH will become famous soon enough
If you have a magnesium anode, there is no need to remove the zinc anode.

The magnesium anode will be 'less noble' in comparison to the zinc anode .... the magnesium anode will be sacrificed (protecting the zinc anode), until the magnesium is fully 'consumed' .... then the zinc will 'take over' as the least noble anode.
Reply With Quote Share with Facebook
  #3  
Old 10-15-2010
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 8 Times in 8 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
Yes, but in fresh water, a zinc anode might not be reactive enough to prevent galvanic corrosion, especially if he has any underwater bits that are aluminum.
__________________
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
  #4  
Old 10-15-2010
zAr zAr is offline
Senior Member
 
Join Date: Feb 2009
Posts: 136
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 6
zAr is on a distinguished road
Yeah, I wouldn't let it get to that point. I'm kinda paranoid about corrosion.

I've been to several sites that say things like "WARNING: Do not mix anode types."

My understanding is along the same lines as what RichH is saying, the least noble metal will just take over. I don't understand why it would be a problem to mix.

By some wild leap of the imagination does mixing metals somehow cause each anode to cancel each other out, effectively rendering you without the protection of either?
__________________
RS
Reply With Quote Share with Facebook
  #5  
Old 10-15-2010
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 6,760
Thanks: 0
Thanked 49 Times in 40 Posts
Rep Power: 6
mitiempo will become famous soon enough
No, the least noble metal is the first to be sacrificed in every case.
__________________
Brian
Living aboard in Victoria Harbour
Reply With Quote Share with Facebook
  #6  
Old 10-15-2010
Gene T's Avatar
Senior Member
 
Join Date: May 2006
Location: Left Coast USA
Posts: 666
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Gene T is on a distinguished road
The least noble metal will be sacrificed first, but adding a more noble metal (an aditional zinc) will increase the decay of the least noble. It that makes sense. So if you use both you will just decay the magnesium anode faster, but then the zinc would start protecting when the magnesium is gone.

At least that is the way I see it.

Gene
__________________

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

Currently in Long Beach, CA
Reply With Quote Share with Facebook
  #7  
Old 10-15-2010
hellosailor's Avatar
Senior Member
 
Join Date: Apr 2006
Posts: 10,050
Thanks: 0
Thanked 50 Times in 49 Posts
Rep Power: 10
hellosailor has a spectacular aura about hellosailor has a spectacular aura about
Rob, I'll bet that if you hit each one with a wire wheel or cutting disc, the sparks that they throw are different in size, color, and shape. Spark tests are a pretty simple way to tell metals apart, take a look on the web & I'll bet you can find pictures of what each look like. (Or compare /vs/ a new one of your choice.)

There are all sorts of ways to identify metals, but this should be one of the simplest--if you're hauled or have them in hand.
Reply With Quote Share with Facebook
  #8  
Old 10-17-2010
zAr zAr is offline
Senior Member
 
Join Date: Feb 2009
Posts: 136
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 6
zAr is on a distinguished road
Quote:
Originally Posted by hellosailor View Post
Rob, I'll bet that if you hit each one with a wire wheel or cutting disc, the sparks that they throw are different in size, color, and shape. Spark tests are a pretty simple way to tell metals apart, take a look on the web & I'll bet you can find pictures of what each look like. (Or compare /vs/ a new one of your choice.)
Well, I did do a search and apparently the sparks are too similar, but magnesium does catch fire, so that's something. One source said to heat the metal, then add water, if it burns down the shop then it was magnesium.
I could also take some shavings and try to burn them...zinc won't burn. Another test is electrical, but you need to immerse the part in water. Most tests seem to be chemical, using an acid or alkali..

All of which is far too complicated, so when I'm hauled out I'll just instruct the yard to drill out the anode of unknown composition.

Gene: I'm not sure how adding a more noble anode would increase the rate of decay of the least noble anode?
__________________
RS
Reply With Quote Share with Facebook
  #9  
Old 10-17-2010
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: 1,992
Thanks: 2
Thanked 15 Times in 15 Posts
Rep Power: 12
Fstbttms is on a distinguished road
Quote:
Originally Posted by zAr View Post
Follow up question: How can you tell which type is being used?
If you were to hold both anodes in either hand, comparing weight, it would be obvious which is which. Magnesium anodes are extremely light while zinc anodes are exactly the opposite.
Reply With Quote Share with Facebook
  #10  
Old 10-17-2010
Gene T's Avatar
Senior Member
 
Join Date: May 2006
Location: Left Coast USA
Posts: 666
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Gene T is on a distinguished road
Quote:
Originally Posted by zAr View Post
Gene: I'm not sure how adding a more noble anode would increase the rate of decay of the least noble anode?
Two different metals in an electrolyte create a battery. Even though the potential between the two metals might be close electrolysis is still created between them.

Gene
__________________

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

Currently in Long Beach, CA
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
Anodes disappearing quickly steveg353 Gear & Maintenance 32 10-18-2010 06:12 PM
Pacific Seacraft 40 Anodes Avocette Pacific Seacraft 4 02-25-2010 03:24 PM
Zinc Anodes johnseattle General Discussion (sailing related) 3 12-20-2009 11:24 PM
Anodes warwicksail Gear & Maintenance 2 12-28-2007 07:28 PM
Anodes & Corrosion serendib Gear & Maintenance 6 07-30-2006 03:15 PM


All times are GMT -4. The time now is 01:22 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