Rust proofing after cutting threads

Discussion in 'Wooden Boat Building and Restoration' started by scott2640, Apr 4, 2017.

  1. scott2640
    Joined: Dec 2016
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    scott2640 Junior Member

    I need to make up several very long bolts for my build (some as big as 40 inches). I found a good price on 5/8" galvanized bar stock that I can cut to length and thread to my specifications. I don't want to use SB rod, sticker shock!

    After I cut the threads, and there by remove all the galvanizing from the bar stock in the threaded area, what is the best way to treat the exposed steel to prevent/avoid the threads rusting? Epoxy? Paint?

    appreciate the input.
     
  2. PAR
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    PAR Yacht Designer/Builder

    Where will these bolts be located on the boat? If this is some deadwood drifts or through bolts for your Duck, then George would likely recommend to butter them up with asphalt based roofing tar, as they're driven home. After they're through again, more black mamie, fully coating the bar stock, nut and washer assembly.
     
  3. Barry
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    Barry Senior Member

    There are two types of galvanizing, hot dip which is what it means, the rod is immersed into the hot zinc and the other is zinc that has been electroplated on the bolt. Shiny zinc plated bolts are electroplated and the dull grey, rough finish galvanized bolts are hot dipped.

    The hot dipped provides a thicker coating and therefore offer better corrosion resistance.

    Depending on what the bolt is used for, you could cut the threads and then find a company that would hot dip plate the entire bolt. Ie purchase normal bar stock cut the threads, hot dip it and away you go. You would have to find out the cost of this and compare it to stainless.

    If you go this route the nuts for a hot dipped bolt are machined a bit larger than stock nuts to enable the thicker coating on the bar stock threads to remain intact.

    You should determine if your galvanized bar stock is hot dipped or electroplated.

    The target should be hot dipped for a marine application.

    I would google bolt hot dipped bolt manufacturers to see what the cost is compared to stainless. Many dock/piling companies use hot dipped long bolts, and perhaps they may be a source
     
  4. Easy Rider
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    Easy Rider Senior Member

    I'll add pine tar.
     
  5. Barry
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    Barry Senior Member

  6. Willco
    Joined: Jun 2017
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    Willco New Member

    This is what I would suggest as well then you will not exposed the raw steel. You could look up "galvanized ready rod" as well; I've seen this in 48" lengths
     
  7. gonzo
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    gonzo Senior Member

    If you galvanized a thread, it should be cut smaller. Otherwise,the finished diameter will be too large. Deduct the thickness of the galvanizing.
     
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  8. Mr Efficiency
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    Mr Efficiency Senior Member

    It should be possible to buy galv threaded rod, Not much point buying galv plain rod and threading it yourself, that I can see.
     
  9. PAR
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    PAR Yacht Designer/Builder

    Getting things hot dipped isn't that hard. Galvanized threads are generally cut more "generous" compaired to a typical rolled thread bolt, as Gonzo points out. Make up your bolts, cut the threads, pound over some heads and get them dipped.
     
  10. gonzo
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    gonzo Senior Member

    We are getting 6' x 25' floating dock metal frames hot dipped for under $200. It can't be too much for a few rods. However, if you are going to get them galvanized after threading, it makes no sense to buy galvanized rod. Buy plain steel rod instead.
     
  11. PAR
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    PAR Yacht Designer/Builder

    Yeah, that's my experience with hot dipping too Gonzo.
     
  12. pauloman
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    pauloman Epoxy Vendor

    google aluthane
     
  13. sdowney717
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    sdowney717 Senior Member

    Any water resistant-proof substance is going to help a lot.
    A marine grease could work. The marine grease is good as it does not wash off with water. You can heat shrink tubing over exposed greased threads.

    I have noticed the Rectorseal T plus 2 teflon pipe sealer is waterproof. I have been using this now on rubber hoses, keeps them from sticking to pipe nipples. Also on bolt threads, keeps away rust, keeps nuts from rusting to the bolt, keeps water out.

    RectorSeal T Plus 2 4 oz. Teflon Pipe-Thread Sealant-23631 - The Home Depot https://www.homedepot.com/p/RectorSeal-T-Plus-2-4-oz-Teflon-Pipe-Thread-Sealant-23631/100201204
     
  14. baeckmo
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    baeckmo Hydrodynamics

    Agree with PAR and Gonzo, but I'd also like to propose the use of raw linseed oil for corrosion protection. It creeps into every corner and crevice, and "dries" by oxidation, not by giving off solubles. During oxidation, it will swell, thereby effectively blocking any access of oxygen and moist.
     

  15. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    what about 316 cold rolled?

    Too weak?

    Stringy bugger for sure, but if it was 5/8" maybe it'd meet your strength req and anything you cut is ready now
     
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