Fairing Stainless Steel with epoxy

Discussion in 'Materials' started by mydauphin, Mar 9, 2009.

  1. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    I have couple of SS rudders. The welds around area where shaft meets blade are not smooth, they have splatter marks. Just not perfect. There is also some little crevices that can lead to corrosion. I was thinking of acid washing, then fairing with epoxy filler, sanding and then painting rudders with epoxy paint. Then perhaps antifouling. So I would be treating it like aluminum. I know SS need oxygen to prevent corrosion and that encasing can actual make corrosion worse. Any ideas on this, is there anything I can do to Stainless like zinc chromate to mitigate problem. thanks
     
  2. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    Better off to buff off the spatter and have someone TIG the crevices and then buff smooth...leave the stainless uncovered.

    Steve
     
  3. apex1

    apex1 Guest

    As lewis mentioned, get it welded proper, think about electropolishing then, we have only positive experience with El. polish treatment. Do not cover it, you know why.
    Regards
    Richard
     
  4. Guest62110524

    Guest62110524 Previous Member

    please dont buff ss, yes fill with weld, and then abrade as rough as you can , sandblasting is best
    All my alloy yachts have ss rudders ,so many times I have been there and done that as they say:))
    anyways its is possible to accurately fair in the skin like this, to late now, but next time eh♠
     
    Last edited: Jun 21, 2010
  5. apex1

    apex1 Guest

    Stu, do you mean polishing when you say buff? If so, why not? We made the experience that El polishing gives the best density to the surface, therefore the best corrosion resistance.
    Regards
    Richard
     
  6. Guest62110524

    Guest62110524 Previous Member

    rich, if you tried stick paint to a polished rail it would fall off, buff in my lingo means polish, maybe in other places it means abrade? so abrade as much as possible, prime and then do your high build paint, or use altex number one, and just build it to say 250microns, then antifoul when tacky
    maybe it's just different terminology
     
  7. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    If the boat is to live in the water paint it as Lazyjack says, if it is taken out of the water, polish it.
     
  8. apex1

    apex1 Guest

    Welcome Stu,
    have understood right, that you meant polish. Same terminology! But we just El. polish our ss trimtabs and rudder shaft and do´nt apply paint.
    Naturally if you MUST apply paint on ss you have to blast or abrade prior to priming / painting.
    Regards
    Richard
     
  9. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    So should I paint or not...Doesn't welding affect Stainless. I have seen zincs on some SS rudders and not on some....thanks again
     
  10. Guest62110524

    Guest62110524 Previous Member

    yes if you are in water paint,
    what is your boat? wood? steel? cant advise much abt Zn until we know
     
  11. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    If the welds do not affect the performance, best to have a few sacrificial anodes. Since you haven't mentioned the material of the boat, as noted above, you really need to consider the "whole" environment:boat material, shaft, prop, fastenings etc. If you paint it when the paint eventually peels off, as it will, you're back to square one.
    If your whole boat is a mixture, then you'll need anodes of some sort anyway.
     
  12. mydauphin
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    mydauphin Senior Member

    Sorry about missing this most important information. My Boat is Aluminum, zinc chromated, epoxyied, faired and painted. Bottom paint will not have any copper. Propellers are bronze, no choice on that. SS shafts. Drives are fixed surface piercing, Rudder are right behind barely in water. Boat will be used not everyday, not trailable but not run everyday. Mainly at anchor with many trip in between, I hope.

    Thank
     
  13. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Well considering the cornucopia of metals you have, i assume you have some protection, such as anodes of some description somewhere?.. But if the performance of the rudders are not really affected by the welds, why worry? You have many other potential sources of corrosion not just the rudder.

    What type of SS is the rudder 316L?
     
  14. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    The rudder is 316L ... It is a matter of efficiency and looks really... yeah a few zincs
     

  15. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Well..since you already have zincs in the aft end and the rudder is made from 316L, other than poor/sloppy workmanship in the weld, is it really worth all the hassle to correct?
    Since once you address the problem, the underlying corrosive environment and electrical potentials still exits, you can't change that. Sure you may 'extend' the life of the weld, potentially. But considering everything else, if the rudder is easy to inspect, i would just leave all as is, maybe add one more anode perhaps, if you're still concerned.
     
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