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superkraut
Joined: 18 Mar 2001 Posts: 346
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Posted: Tue Jul 23, 2013 1:30 pm Post subject: |
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with the "right" sort of impact, there can be lots of bending force on the fin bolt, particularly with a Powerbox!
http://www.boardlady.com/4712.htm |
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swchandler
Joined: 08 Nov 1993 Posts: 10588
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Posted: Tue Jul 23, 2013 2:51 pm Post subject: |
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For many years I was involved in the procurement of high tech machine parts for the defense industry. We used to make a proximity fuse for the Navy's Stinger missiles where the housing was manufactured from a high grade of stainless steel. After machining, the housing was electroetched and then passivated to remove any exposed ferrites and to oxidize the surface.
What I notice often with SS screws and other components used for windsurfing is that exposed ferrites lead to corrosion and rust staining of the surface. While I've never had a problem with failure of these components, you can see how the passivation layer has been compromised. |
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keycocker
Joined: 10 Jul 2005 Posts: 3598
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Posted: Tue Jul 23, 2013 5:06 pm Post subject: |
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To further rigits excellent explanation - the crevice corrosion can be much worse in SS than other steel. Other steel gets a thin layer of rust over a large area. When the surface layer is compromised on SS in a tiny spot, all the electrochemical action is focused on a tiny spot so corrosion goes deeper and is not as visible on the surface as a big blotchy rust spot would be.
This can result in surprise failures of nice shiny parts, a real problem on boats. |
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afolander
Joined: 22 Jul 2002 Posts: 74
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Posted: Wed Jul 24, 2013 12:17 am Post subject: |
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I think a more likely failure mode is chloride stress corrosion cracking combined with fatigue once the crack got big enough. This failure mode does not usually affect stainless steels at ambient temps except where high residual stresses are present, i.e. fasteners.
If it was crevice corrosion I think you would see more evidence of metal etching on the crack surface and more than one thread affected. |
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spennie
Joined: 13 Oct 1995 Posts: 975 Location: Thousand Oaks, CA
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Posted: Wed Jul 24, 2013 7:17 am Post subject: |
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Who would have guessed the world was full of windsurfing metallurgists? _________________ Spennie the Wind Junkie
www.WindJunkie.net |
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Georges
Joined: 10 Apr 2000 Posts: 249
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Posted: Wed Jul 24, 2013 9:01 am Post subject: |
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I will buy you a new screw if it brakes THIS thread. |
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whitevan01
Joined: 29 Jun 2007 Posts: 607
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Posted: Wed Jul 24, 2013 10:28 am Post subject: |
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kiters: cool dudes
surfers: ultimate cool dudes
windsurfers: nerds |
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afolander
Joined: 22 Jul 2002 Posts: 74
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Posted: Wed Jul 24, 2013 2:23 pm Post subject: |
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Guess I will never be an "ultimate cool" nerd. |
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andydavis
Joined: 11 Apr 1999 Posts: 319 Location: Point Isabel
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Posted: Wed Jul 24, 2013 3:10 pm Post subject: |
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whitevan01 wrote: | kiters: cool dudes
surfers: ultimate cool dudes
windsurfers: nerds |
why you harshing on us? |
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jibemeister
Joined: 27 Sep 1994 Posts: 18
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Posted: Wed Jul 24, 2013 5:02 pm Post subject: |
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Sounds like some sort of STD. |
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