Reply
 
Thread Tools Search this Thread Display Modes
 
Old 09-25-2019, 01:33 PM   #1
Member
 
City: portsmouth
Country: United Kingdom
Vessel Name: Chartwell
Vessel Model: GB 36 Classic
Join Date: Mar 2017
Posts: 5
Anode bolts

Hi I have a 1992 GB 36 currently in the South of France in a boatyard.

Today I took my port hull anode off and found the bolts are corroded such that they look like they have been acting as an anode.

The starboard side bolts look fine. I am obviously going to renew the defective bolts but would like to know what may have caused this if anyone has any idea's so that I can remedy.

I will try and attach pictures.

Thank you for your assistance.

Regards Fred
Attached Thumbnails
Click image for larger version

Name:	20190925_151623.jpg
Views:	34
Size:	191.3 KB
ID:	94388   Click image for larger version

Name:	20190925_151607.jpg
Views:	30
Size:	196.8 KB
ID:	94389  
__________________
Advertisement

Chartwell is offline   Reply With Quote
Old 09-25-2019, 02:17 PM   #2
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,630
If those are (were) stainless, use silicon bronze. That's what I used for decades on a transom mount Divers Dream.

PS; make sure the bonding wires are intact. The install looks a bit peculiar. I use studs, that are fastened with nuts and washers on each side of the hull. Then the zinc is attached with nuts 5 and 6.
__________________

diver dave is online now   Reply With Quote
Old 09-25-2019, 02:43 PM   #3
Member
 
City: portsmouth
Country: United Kingdom
Vessel Name: Chartwell
Vessel Model: GB 36 Classic
Join Date: Mar 2017
Posts: 5
Dave thanks for the reply. I think that they are stainless and these where studs as you describe. They where fastened with nuts and a fixed washer each side of the hull.


Quote:
Originally Posted by diver dave View Post
If those are (were) stainless, use silicon bronze. That's what I used for decades on a transom mount Divers Dream.

PS; make sure the bonding wires are intact. The install looks a bit peculiar. I use studs, that are fastened with nuts and washers on each side of the hull. Then the zinc is attached with nuts 5 and 6.
Chartwell is offline   Reply With Quote
Old 09-25-2019, 02:43 PM   #4
Guru
 
Comodave's Avatar
 
City: Au Gres, MI
Country: US
Vessel Name: Never Say Never
Vessel Model: President 41 DC
Join Date: Jul 2015
Posts: 5,510
Agree with Diver Dave. In addition I would check your bonding system if only one side corroded away. The side that didnít corrode may not be connected well so it did not corrode. Or maybe the bolts that didnít corrode may be bronze.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you arenít one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 09-25-2019, 02:47 PM   #5
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,630
Forgot one thing. Is the transom wood or composite or ?? If wet wood, I can see that as a problem with long term contact with some SS grades. Dry and bed the new stuff.
diver dave is online now   Reply With Quote
Old 09-25-2019, 02:54 PM   #6
Member
 
City: portsmouth
Country: United Kingdom
Vessel Name: Chartwell
Vessel Model: GB 36 Classic
Join Date: Mar 2017
Posts: 5
The hull is GRP. Will check the continuity on the other side tomorrow.
Chartwell is offline   Reply With Quote
Old 09-25-2019, 03:04 PM   #7
Guru
 
Comodave's Avatar
 
City: Au Gres, MI
Country: US
Vessel Name: Never Say Never
Vessel Model: President 41 DC
Join Date: Jul 2015
Posts: 5,510
It should be less than 1 ohm resistance in the bonding system.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you arenít one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 09-26-2019, 09:17 AM   #8
Member
 
City: portsmouth
Country: United Kingdom
Vessel Name: Chartwell
Vessel Model: GB 36 Classic
Join Date: Mar 2017
Posts: 5
Anode bolts

Hi guys I put a magnet on the anode studs today to check composition. They are not stainless. Should I now consider changing the corroded ones for stainless and also change the as yet undamaged starboard ones.

Also checked continuity between props and anode studs . It is below 1 ohm.

Regards Fred
Chartwell is offline   Reply With Quote
Old 09-26-2019, 09:29 AM   #9
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,630
fyi, a lot of stainless alloys are magnetic, some are slightly magnetic, some are non-magnetic. Some will change magnetic properties upon stress, heat or mechanical.
In any case, try hard to find a threaded rod in SiBronze. My last install took 1/2", but 3/8" may be more appropriate for your case.

https://www.albanycountyfasteners.co...t-lengths.html
diver dave is online now   Reply With Quote
Old 09-26-2019, 10:46 AM   #10
Guru
 
Comodave's Avatar
 
City: Au Gres, MI
Country: US
Vessel Name: Never Say Never
Vessel Model: President 41 DC
Join Date: Jul 2015
Posts: 5,510
Stainless steel can corrode in the absence of oxygen so it isnít the preferred metal for below the waterline. Look up crevice corrosion.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you arenít one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 09-26-2019, 11:21 AM   #11
Guru
 
koliver's Avatar
 
City: Saltspring Island
Country: BC, canada
Vessel Name: Retreat
Vessel Model: C&L 44
Join Date: Nov 2007
Posts: 3,126
Quote:
Originally Posted by Comodave View Post
Stainless steel can corrode in the absence of oxygen so it isnít the preferred metal for below the waterline. Look up crevice corrosion.
Those corroded bolts look like the bolts holding my swimgrid supports onto the transom, NOT bonded to anything, when I removed them after~25 years.
Below the waterline, stainless and suffering from crevice corrosion.

The replacements are above the wl, though after 10 to 15 yrs I had a reason to remove a couple of the bots attaching the swimgrid to the supports, from the top of the swimgrid, and found some that were already suffering a significant amount of crevice corrosion.
__________________

__________________
Keith
koliver is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 07:57 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012
×