Devastatingly sad video: "The End of The Dream" - Page 14 - SailNet Community
 254Likes
Reply
 
LinkBack Thread Tools
post #131 of 187 Old 02-24-2019
Senior Member
 
Join Date: Feb 2010
Location: Narragansett Bay
Posts: 21,360
Thanks: 84
Thanked 605 Times in 581 Posts
Rep Power: 12
   
Re: Devastatingly sad video: "The End of The Dream"

Quote:
Originally Posted by hpeer View Post
....When you weld SS and mild steel there is a very low potential path between them, this ends the corrosion...

I've not heard this before and am trying to make sense of it. I can imagine, when two metals are welded, there is no way for an electrolyte to get between them, at the weld, and create a pathway for the galvanic action. However, if you submerged the entire welded item in an electrolyte, I don't see how the weld would prevent galvanic reaction any more than two metals that are bolted together.

I'm currently dealing with the classic galvanic pita on all boats. Stainless steel machine screws, into aluminum. I'm trying to get the aft boom end off and half the screws are too corroded to get them to back out. This only from 14 years of rain water soaking them occasionally.


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

Jeanneau 54DS

In the harsh marine environment, something is always in need of repair. Margaritas fix everything.
Minnewaska is offline  
Sponsored Links
Advertisement
 
post #132 of 187 Old 02-24-2019
Senior Member
 
jvlassak's Avatar
 
Join Date: Sep 2009
Location: Boston area
Posts: 499
Thanks: 47
Thanked 24 Times in 24 Posts
Rep Power: 11
 
Re: Devastatingly sad video: "The End of The Dream"

Quote:
Originally Posted by hpeer View Post
...When you weld SS and mild steel there is a very low potential path between them, this ends the corrosion...
I'm not sure this is a correct statement. My understanding of the galvanic corrosion process is as follows: The ion exchange occurs at the interface between the metals and the electrolyte, seawater in this case. For this process to proceed, the metals have to be able to transfer electrons as well, which can only happen if the metals are physically connected by a conductor. If the metals are welded, that path is a very low resistance path making the electron transfer that much easier. If electron transfer is easy, the galvanic reaction can proceed. Galvanic corrosion is a real concern for welds. Depending on what metals are involved, it is also possible to generate hydrogen, which can lead to hydrogen embrittlement, a much worse failure mechanism than corrosion.


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


1995 Pacific Seacraft 34
Iphigenia
jvlassak is online now  
post #133 of 187 Old 02-24-2019
Dirt Free
 
boatpoker's Avatar
 
Join Date: Jul 2008
Location: Toronto
Posts: 2,642
Thanks: 22
Thanked 148 Times in 143 Posts
Rep Power: 12
 
Re: Devastatingly sad video: "The End of The Dream"

Quote:
Originally Posted by Minnewaska View Post
I've not heard this before and am trying to make sense of it. I can imagine, when two metals are welded, there is no way for an electrolyte to get between them, at the weld, and create a pathway for the galvanic action. However, if you submerged the entire welded item in an electrolyte, I don't see how the weld would prevent galvanic reaction any more than two metals that are bolted together.
No need for immersion. A single drop of water across the weld to both metals completes the galvanic path.

The hysterical laughter you hear as you drive a way in your"new" boat ..... is the seller.
boatpoker is online now  
 
post #134 of 187 Old 02-24-2019
Senior Member
 
jvlassak's Avatar
 
Join Date: Sep 2009
Location: Boston area
Posts: 499
Thanks: 47
Thanked 24 Times in 24 Posts
Rep Power: 11
 
Re: Devastatingly sad video: "The End of The Dream"

Quote:
Originally Posted by boatpoker View Post
No need for immersion. A single drop of water across the weld to both metals completes the galvanic path.
That's right, that's all that's needed.


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


1995 Pacific Seacraft 34
Iphigenia
jvlassak is online now  
post #135 of 187 Old 02-24-2019
Senior Member
 
hpeer's Avatar
 
Join Date: May 2005
Location: Onboard
Posts: 1,760
Thanks: 19
Thanked 53 Times in 53 Posts
Rep Power: 16
 
Re: Devastatingly sad video: "The End of The Dream"

Not arguing that if you immerse it in electrolyte you will have a problem. I’m talking about in “dry” locations. And no location on a boat is truly dry. But in any case, above water line applications.

I’m not sufficiently well versed to argue the matter out. I’m simply reporting what I observe all too often in practical application.

In this particular case I’m supporting the idea that a SS tank in an Aluminum keel is a bad idea.

I’m also reporting I observe corrosion where two materials come close together.

I may be wrong in my approach to a fix. When you say in “certain metals” you cause embrittlement, which metals? And what is the rate of degradation? If it’s 50 years I don’t care as long as it stops or slows rust.

P.S. I just did a quick internet search and it seems that welding 316 to mild steel is a very common practice with no special warnings, including on boats.

33' Brewer, Murray 33, steel cutter
44' Pape, Steelmaid, cc steel cutter

Last edited by hpeer; 02-24-2019 at 12:29 PM.
hpeer is online now  
post #136 of 187 Old 02-24-2019
Old soul
 
MikeOReilly's Avatar
 
Join Date: Apr 2010
Location: Wherever I am
Posts: 4,433
Thanks: 268
Thanked 205 Times in 192 Posts
Rep Power: 11
 
Re: Devastatingly sad video: "The End of The Dream"

All this discussion reinforces my view that you really need to know what youíre doing to own a metal boat, and most especially an Al one. Or indeed a wood-hull boat.

In one of the linked videos I was really struck by how little research or thought our protaganist did before deciding that she must have a metal boat. Iím all for frugal cruising, but one basic lesson of this life is that you gotta do your research before making big decisions. I was pretty unimpressed with her explanation of ďwhy this boat.Ē
MarkofSeaLife likes this.

Why go fast, when you can go slow.
BLOG:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
MikeOReilly is online now  
post #137 of 187 Old 02-24-2019
Dirt Free
 
boatpoker's Avatar
 
Join Date: Jul 2008
Location: Toronto
Posts: 2,642
Thanks: 22
Thanked 148 Times in 143 Posts
Rep Power: 12
 
Re: Devastatingly sad video: "The End of The Dream"

Quote:
Originally Posted by hpeer View Post
Not arguing that if you immerse it in electrolyte you will have a problem. Iím talking about in ďdryĒ locations. And no location on a boat is truly dry. But in any case, above water line applications.

Iím not sufficiently well versed to argue the matter out. Iím simply reporting what I observe all too often in practical application.

In this particular case Iím supporting the idea that a SS tank in an Aluminum keel is a bad idea.

Iím also reporting I observe corrosion where two materials come close together.

I may be wrong in my approach to a fix. When you say in ďcertain metalsĒ you cause embrittlement, which metals? And what is the rate of degradation? If itís 50 years I donít care as long as it stops or slows rust.

P.S. I just did a quick internet search and it seems that welding 316 to mild steel is a very common practice with no special warnings, including on boats.
As a Certified Marine Corrosion Analyst I'd suggest you don't believe everything you read on the internet.

The hysterical laughter you hear as you drive a way in your"new" boat ..... is the seller.
boatpoker is online now  
post #138 of 187 Old 02-24-2019
Dirt Free
 
boatpoker's Avatar
 
Join Date: Jul 2008
Location: Toronto
Posts: 2,642
Thanks: 22
Thanked 148 Times in 143 Posts
Rep Power: 12
 
Re: Devastatingly sad video: "The End of The Dream"

Quote:
Originally Posted by MikeOReilly View Post
All this discussion reinforces my view that you really need to know what youíre doing to own a metal boat, and most especially an Al one.
Absolutely correct. Aluminum boats can be destroyed in a mattter of days by amateur electricians.
MikeOReilly likes this.

The hysterical laughter you hear as you drive a way in your"new" boat ..... is the seller.
boatpoker is online now  
post #139 of 187 Old 02-24-2019
Senior Member
 
Join Date: Feb 2010
Location: Narragansett Bay
Posts: 21,360
Thanks: 84
Thanked 605 Times in 581 Posts
Rep Power: 12
   
Re: Devastatingly sad video: "The End of The Dream"

Quote:
Originally Posted by boatpoker View Post
No need for immersion. A single drop of water across the weld to both metals completes the galvanic path.
Understood. Poor choice of words, I simply meant an electrolyte spanned the two metals.


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

Jeanneau 54DS

In the harsh marine environment, something is always in need of repair. Margaritas fix everything.
Minnewaska is offline  
post #140 of 187 Old 02-24-2019
Senior Member
 
Join Date: Feb 2010
Location: Narragansett Bay
Posts: 21,360
Thanks: 84
Thanked 605 Times in 581 Posts
Rep Power: 12
   
Re: Devastatingly sad video: "The End of The Dream"

Quote:
Originally Posted by hpeer View Post
....Iím talking about in ďdryĒ locations. And no location on a boat is truly dry. But in any case, above water line applications.....
If you really meant dry, then sure, no corrosion at the weld. You need an electrolyte, not simply touching metals.

It's very common to have stainless steel parts in contact with aluminum masts. They are intermittently exposed to an electrolyte (rain or spray) and still corrode. Albeit very slowly. I will be treating the screws I'm trying to remove right now with TefGel, before they go back in.
mbianka likes this.


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

Jeanneau 54DS

In the harsh marine environment, something is always in need of repair. Margaritas fix everything.
Minnewaska is offline  
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
A sad end for a fine boat PaulinVictoria C & C 31 08-22-2014 10:56 PM
VIDEO: Coast Guard Academy Welcomes "Blue Goose" and "Stormy Petrel" - Patch.com NewsReader News Feeds 0 07-28-2012 07:50 AM
What a waste..Sad, very sad PCP General Discussion (sailing related) 27 12-17-2010 12:33 AM
A sad tale of a beached sailboat swallowed by the sea. Video. AllThumbs General Discussion (sailing related) 19 11-24-2008 08:21 PM
Great video on end-to-end splice arf145 Gear & Maintenance 0 06-04-2008 03:34 PM

Posting Rules  
You may post new threads
You may 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 On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome