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Stainless bolts below the waterline?

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  • August 10, 2012 12:10 PM
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    Message # 1043738
    Anonymous member

    All,

    I am wondering if it is necessary to replace my old bronze hardware below the waterline with new bronze, or is stainless acceptable.

    Let me explain: I am replacing my seacocks and my rudder is removed.  The seacock bolts will be countersunk into the hull, bedded, glassed over, and faired.  The rudder gudgeons bolts will bedded and glassed over.

    So, what is the verdict: Bronze or Stainless?

    Tyler
  • August 10, 2012 1:17 PM
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    Reply # 1043808 on 1043738
    Anonymous
    I would use bronze. Especially if glassing over... 
    Also, I think using stainless screws with bronze seacocks will result in the stainless being the sacrificial part (less noble)

    my .02c
  • August 10, 2012 2:14 PM
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    Reply # 1043841 on 1043738
    Anonymous member

    Marelon seacocks. . . stainless being less noble is a non-issue.

    T.
  • August 10, 2012 2:40 PM
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    Reply # 1043856 on 1043738
    Anonymous
    I'm no expert on the whole thing but my understanding is that stainless steel is corrosion resistant because it has a high amount of chromium in it which forms a protective oxide when exposed to oxygen. 

    If you encapsulate the SS bolts, they will not breath and the protective oxide layer will eventually fail and then you'd have bolts that aren't as strong and just as vulnerable to corrosion as normal steel. 

    For that reason, I'd suggest going with bronze. 
  • August 11, 2012 7:43 AM
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    Reply # 1044250 on 1043856
    Anonymous
    Tate McDaniel wrote:....chromium in it which forms a protective oxide when exposed to oxygen. 

    If you encapsulate the SS bolts, they will not breath and the protective oxide layer will eventually fail
      
    Would this also apply to the stainless bobstay fitting if it is underwater? 
  • August 11, 2012 8:36 AM
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    Reply # 1044278 on 1044250
    Anonymous member (Administrator)
    Eric Olander wrote:
    Tate McDaniel wrote:....chromium in it which forms a protective oxide when exposed to oxygen. 

    If you encapsulate the SS bolts, they will not breath and the protective oxide layer will eventually fail
      
    Would this also apply to the stainless bobstay fitting if it is underwater? 


    While the first 200 or so Westsails had stainless steel gudgeons followed by fiberglass -- I use the rule that below and near the water line use bronze (not brass).  I also removed my bronze seacocks and replaced with marelon seacocks. 

    A stainless bobstay underwater or near the water will need a zinc to prevent electrolysis.

    Here is a link to Items that break - (members only) and in the middle there is what I believe is a bobstay that failed due to electrolysis.

    Jay

    Last modified: August 11, 2012 8:46 AM | Anonymous member (Administrator)
  • August 11, 2012 1:45 PM
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    Reply # 1044427 on 1044250
    Anonymous
    Eric Olander wrote:
    Tate McDaniel wrote:....chromium in it which forms a protective oxide when exposed to oxygen. 

    If you encapsulate the SS bolts, they will not breath and the protective oxide layer will eventually fail
      
    Would this also apply to the stainless bobstay fitting if it is underwater? 

    It isn't the water that worried me about the oxygen starvation.  Water has plenty of oxygen in it so that makes SS a fine component for underwater.  What concerns me is encapsulating the SS in either glass/epoxy/5200/etc.  Stuff that won't let it "breath" at all. 
     
    Last modified: August 11, 2012 3:28 PM | Anonymous member (Administrator)
  • August 11, 2012 3:29 PM
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    Reply # 1044474 on 1044427
    Anonymous member (Administrator)
    Tate McDaniel wrote:
    Eric Olander wrote:
    Tate McDaniel wrote:....chromium in it which forms a protective oxide when exposed to oxygen. 

    If you encapsulate the SS bolts, they will not breath and the protective oxide layer will eventually fail
      
    Would this also apply to the stainless bobstay fitting if it is underwater? 

    It isn't the water that worried me about the oxygen starvation.  Water has plenty of oxygen in it so that makes SS a fine component for underwater.  What concerns me is encapsulating the SS in either glass/epoxy/5200/etc.  Stuff that won't let it "breath" at all. 

     
    I agree that O2 starvation as the issue also different waters have different O2 concentrations.
     
    Jay
  • August 20, 2012 5:51 PM
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    Reply # 1051994 on 1043738
    Deleted user
    Where would I find zincs to fit on a bobstay?
  • August 20, 2012 7:54 PM
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    Reply # 1052082 on 1043738
    Anonymous member (Administrator)

    I find the tear drop shape or a small round zinc - one on each side works - try online marine suppliers.
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