Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 27-09-2019, 21:14   #16
Moderator Emeritus
 
sailorchic34's Avatar

Cruisers Forum Supporter

Join Date: Feb 2011
Location: SF Bay Area
Boat: Islander 34
Posts: 5,486
Re: How to stop crevice corrosion?

Quote:
Originally Posted by redsky49 View Post
Could the deck mounted flange be constructed of a material other than stainless steel?
It looks like a casting, plated bronze perhaps??
That is actually my thought. I think that ring it's just Chrome plated Steel. It looks hollow inside.
sailorchic34 is offline   Reply With Quote
Old 27-09-2019, 21:49   #17
Moderator
 
Jim Cate's Avatar

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 21,151
Re: How to stop crevice corrosion?

Quote:
Originally Posted by Wotname View Post
Jim, you gotta look at the big picture and not cherry pick the words. The full description was "air carried low level current (stray current)". The stray current is what gives meaning to the phrase - you gotta know your electrical theory to understand what is happening.

You see real (or proper) current is the current that runs around metal wire and it is kept there by the insulation on the wire but at the terminals of the wire, most folk don't cover them with the right stuff. Some even leave them exposed to the air and this is where the current strays off from the wire. It is called stray current and it then travels around wherever the air carries it. Of course it is low level unless there is a significant thermal updraft that carries it higher.

I'm not sure but I think that if enough of it is carried aloft, it stays there until it rains which washes it out and back to the ground - we call it lightning

By keeping a weather eye on the covering of the electrical terminals, you can stop it straying into the air and causing problems for other nearby boaters.

Simple really
Damn, Wottie, I'm sure glad that you can explain things so well that even I can understand awfully complex stuff like this!

Outstanding effort, old friend!

Jim
__________________
Jim and Ann s/v Insatiable II, lying Port Cygnet Tasmania once again.
Jim Cate is offline   Reply With Quote
Old 27-09-2019, 22:01   #18
Registered User

Join Date: Oct 2011
Location: Wherever the wind takes me
Boat: Bristol 41.1
Posts: 1,006
Re: How to stop crevice corrosion?

Just for curious minds, have you checked these parts with a magnetic?
redsky49 is offline   Reply With Quote
Old 27-09-2019, 22:10   #19
Moderator and Certifiable Refitter
 
Wotname's Avatar

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,301
Re: How to stop crevice corrosion?

Quote:
Originally Posted by sailorchic34 View Post
A lovely discription. Wish i had thought of it....
Well I can't take all the credit!

Some smart guys like Alessandro Giuseppe Antonio Anastasio Volta, André-Marie Ampère and Georg Simon Ohm did most of the onerous thinking and I just put together in a language more comprehensible for the internet era - crikey, even wikipedia isn't across the exquisite attributes of stray current atmospheric channelling and the defilement and vitiation it causes to cowl vents.

The OP is lucky to have caught it in time.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Old 27-09-2019, 23:26   #20
Registered User

Join Date: Apr 2007
Location: Australia
Boat: Island Packet 40
Posts: 6,432
Images: 7
Re: How to stop crevice corrosion?

If the mob get wind of that one she could go viral.

There is probably a crack there.

I would clean off the rust with a rust remover, give it a spray of Marine Penetrol or boiled linseed oil or epoxy sealer and wipe off the excess. Whatever you use needs to be thin so that capillary action will draw it into the crack. You will probably need to do it regularly to keep the rust away.

Getting back to the airborne electrolysis theory. Could you please give us a run down on the physics using Maxwell's field equations. Might make it a bit easier to understand if expressed mathematically.
RaymondR is offline   Reply With Quote
Old 28-09-2019, 11:33   #21
Marine Service Provider
 
boatpoker's Avatar

Join Date: Nov 2008
Location: Port Credit, Ontario or Bahamas
Boat: Benford 38 Fantail Cruiser
Posts: 7,060
Re: How to stop crevice corrosion?

I believe Tesla invented the tin foil hat specifically for "electrolysis" or more specifically for those that believe that it is a corrosion process.
__________________
If you're not laughing, you're not doin' it right.
boatpoker is offline   Reply With Quote
Old 28-09-2019, 14:18   #22
Registered User

Join Date: Dec 2017
Posts: 8
Re: How to stop crevice corrosion?

It looks like chrome plated steel with a bit of undercut on the weld. Just clean it periodically as outlined above. There are numerous kinds of stainless that have magnetic properties, the old magnet trick doesn't apply to all stainless.
Old_Geezer is offline   Reply With Quote
Old 28-09-2019, 19:16   #23
Registered User

Join Date: Apr 2007
Location: Australia
Boat: Island Packet 40
Posts: 6,432
Images: 7
Re: How to stop crevice corrosion?

electrolysis, galvanic, to a yachty it's all the same. We don't get uptight about a bit of vernacular being introduced into the nomenclature ----- or should that be terminology.
RaymondR is offline   Reply With Quote
Old 28-09-2019, 19:30   #24
Registered User
 
AKA-None's Avatar

Join Date: Oct 2013
Location: Lake City MN
Boat: C&C 27 Mk III
Posts: 2,647
Re: How to stop crevice corrosion?

Is this the joke thread?
__________________
Special knowledge can be a terrible disadvantage if it leads you too far along a path that you cannot explain anymore.
Frank Herbert 'Dune'
AKA-None is offline   Reply With Quote
Old 28-09-2019, 20:43   #25
Moderator
 
Jim Cate's Avatar

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 21,151
Re: How to stop crevice corrosion?

Quote:
Originally Posted by AKA-None View Post
Is this the joke thread?
No, but it does have a laughable poster...

Jim
__________________
Jim and Ann s/v Insatiable II, lying Port Cygnet Tasmania once again.
Jim Cate is offline   Reply With Quote
Old 28-09-2019, 22:57   #26
Registered User
 
Uncle Bob's Avatar

Join Date: May 2010
Location: Sydney Australia
Boat: Fisher pilothouse sloop 32'
Posts: 3,416
Re: How to stop crevice corrosion?

Quote:
Originally Posted by Jim Cate View Post
No, but it does have a laughable poster...

Jim
Oh Jim, you're so cruel. But so accurate.
__________________
Rob aka Uncle Bob Sydney Australia.

Life is 10% the cards you are dealt, 90% how you play em
Uncle Bob is offline   Reply With Quote
Old 30-09-2019, 00:30   #27
Registered User

Join Date: Apr 2007
Location: Australia
Boat: Island Packet 40
Posts: 6,432
Images: 7
Re: How to stop crevice corrosion?

Well perhaps you folks would like to explain the difference between galvanic and electrolytic action??
RaymondR is offline   Reply With Quote
Old 30-09-2019, 01:35   #28
Moderator and Certifiable Refitter
 
Wotname's Avatar

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,301
Re: How to stop crevice corrosion?

Quote:
Originally Posted by RaymondR View Post
Well perhaps you folks would like to explain the difference between galvanic and electrolytic action??
Is this a trick question???

Assuming the question is genuine, the answer is straightforward.

Galvanic action occurs when two dissimilar metals are placed in conducting medium creating potential difference and current flows between them.

Electrolytic action occurs when two metals are placed in conducting medium and external EMF is applied to them causing current to flow between them.

But I think you know this!
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Old 01-10-2019, 01:25   #29
Registered User

Join Date: Apr 2007
Location: Australia
Boat: Island Packet 40
Posts: 6,432
Images: 7
Re: How to stop crevice corrosion?

Quote:
Originally Posted by Wotname View Post
Is this a trick question???

Assuming the question is genuine, the answer is straightforward.

Galvanic action occurs when two dissimilar metals are placed in conducting medium creating potential difference and current flows between them.

Electrolytic action occurs when two metals are placed in conducting medium and external EMF is applied to them causing current to flow between them.

But I think you know this!
If one wanted to get pedantic about it might one proffer that PbO is not a metal in the lead acid battery or carbon in the zinc carbon battery.

And that molten sodium chloride is neither and it can be electrolysed to produce sodium metal or water to produce hydrogen and oxygen.

and one might propose that One could use the hull of ones steel boat for earth return instead of running twin cable without corrosion problems since two metals are not involved.

To be nasty in return for the pile on I'll promise not to use terms of more than one or two syllables in future if I think you blokes are likely to read them.
RaymondR is offline   Reply With Quote
Old 01-10-2019, 02:33   #30
Moderator and Certifiable Refitter
 
Wotname's Avatar

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,301
Re: How to stop crevice corrosion?

Quote:
Originally Posted by RaymondR View Post
If one wanted to get pedantic about it might one proffer that PbO is not a metal in the lead acid battery or carbon in the zinc carbon battery.

And that molten sodium chloride is neither and it can be electrolysed to produce sodium metal or water to produce hydrogen and oxygen.

and one might propose that One could use the hull of ones steel boat for earth return instead of running twin cable without corrosion problems since two metals are not involved.

To be nasty in return for the pile on I'll promise not to use terms of more than one or two syllables in future if I think you blokes are likely to read them.
Well, I do understand single syllables best
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Reply

Tags
corrosion

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
JB Marine Weld and Crevice Corrosion rognvald Construction, Maintenance & Refit 17 07-07-2014 09:53
Rudder Stock Crevice Corrosion Cruisin Cat Construction, Maintenance & Refit 15 29-04-2013 16:57
Crevice Corrosion On Rudder Stock stevensuf Construction, Maintenance & Refit 4 19-10-2012 12:07
Crevice Corrosion - Is My Rudder Toast ? Matt Johnson Construction, Maintenance & Refit 41 14-11-2011 21:14
Crevice Corrosion Triton318 Construction, Maintenance & Refit 6 05-10-2008 13:37

Advertise Here


All times are GMT -7. The time now is 07:53.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.