Finishing 316L stainless rails

Discussion in 'Boat Design' started by sprit, Oct 8, 2013.

  1. alex n
    Joined: Aug 2013
    Posts: 9
    Likes: 1, Points: 0, Legacy Rep: 23
    Location: new jersey

    alex n Junior Member

    You guys are over engineering a bow rail. How long do mill finished stainless seacocks look nice in an engine room. I have two of them that are pushing 20 years that look like new.
     
  2. Stumble
    Joined: Oct 2008
    Posts: 1,913
    Likes: 73, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    No idea since stainless isn't allowed to be used for sea-cocks (see ABYC H-27, or UL rating 1121 or 618C). Stainless isn't allowed in this application out of concern for crevice corrosion.
     
  3. alex n
    Joined: Aug 2013
    Posts: 9
    Likes: 1, Points: 0, Legacy Rep: 23
    Location: new jersey

    alex n Junior Member

    Well it would still look very nice as a bow rail. No crevice corrosion in that application. 316 would hold up way better than anodized aluminum in my opinion.
     
  4. MikeJohns
    Joined: Aug 2004
    Posts: 3,192
    Likes: 208, Points: 63, Legacy Rep: 2054
    Location: Australia

    MikeJohns Senior Member

    Sure the smoother surface is the perfect finish but there is a big distinction between possible tarnishing and significant corrosion.
    There's a lot of matte finish 316 on vessels that works well and doesn't tarnish, and it is not considered poor practice in the marine industry.

    Significantly rough surfaces ( not just a uniform matte) trap salt from droplet evaporation, and in high humidity that can produce small oxygen starved corrosion cells that will lead eventually to small scale pitting/crevice corrosion. But with an exposed railing its visible and obvious from visible staining and the corrosion rate is so low as to be negligible.

    Structural SS items with significant stresses are polished importantly to relieve the surface of potential stress risers. It makes a big difference.
    But H-27 just refers to UL 1121 which in turn doesn’t say anything specific about stainless steel at all.
    It would surprise me if it did, since if you get specific you’d simply specify the grade of stainless since the corrosion properties vary so much with different alloying.

    With sea cocks it’s the strength we are really concerned with and all commercial vessels have their sea cocks pulled and checked at every survey, so material is not such an issue even for brass.
     
    Last edited: Oct 17, 2013
  5. 1618
    Joined: Oct 2013
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Virginia

    1618 New Member

    They make seacocks out of brass?
     
  6. MikeJohns
    Joined: Aug 2004
    Posts: 3,192
    Likes: 208, Points: 63, Legacy Rep: 2054
    Location: Australia

    MikeJohns Senior Member

    Sure

    They are cheap last at least 5 years before needing replacment and meet both UL 1121 and the European RCD. Though not my choice of material at all. They are installed on a lot of production boats and people really need to be aware of this. Manufacturers just jack up their profit margin by using cheap fittings that are only required to last 5 years under the RCD.

    The idea is as I posted before, is that you pull and inspect your seacocks at haulout or at least sensible to do it every 3 years.

    UL-1121 requires that any brass be able to withstand a specific cracking test but otherwise it's fine to use under that standard and hence under ABYC H-27.
     
  7. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    The chrome plated ss ball style valve seems to need service every year.

    Installed three new one 2 years ago and now i must close them with a steel pipe handle extension.

    Water handling gear is high maintenance
     
  8. MikeJohns
    Joined: Aug 2004
    Posts: 3,192
    Likes: 208, Points: 63, Legacy Rep: 2054
    Location: Australia

    MikeJohns Senior Member

    Michael
    They are chrome plated brass balls not chrome plated stainless steel.

    The quality ball valves use a stainless steel ball and teflon seals, try and avoid the chromed brass balls.
     
  9. pdwiley
    Joined: Jun 2008
    Posts: 1,004
    Likes: 86, Points: 48, Legacy Rep: 933
    Location: Hobart

    pdwiley Senior Member

    Yes, the price difference locally being maybe $15 for the brass ball valves and $85 or more for the 316 ball valves.

    I have the expensive ones. I don't even plan on using a 304 grade one I got off of Ebay (they lied about the grade, I didn't pay).

    WRT the original question, I have zero intention of polishing 18m plus of rail and a pile of stanchions of 316L 20NB Sched 40 pipe. If it rusts, it rusts. I'll worry about it if it happens, which IME with stainless railings, will be approximately never inside my lifetime.

    It would take me less time AND aggravation to replace all the railings in 10 years or so, worst case, than the sheer aggravation involved in polishing them and keeping them nice & shiny. I have better things to do.

    PDW
     
  10. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    I have been usung normal steel chassis valves. Price.

    When painted they hold up well in locations that are not wet. Bilges are normally dry. I believe that the ball is the same spec Regardless of chassis material. The chrome plated ball fouls when stationary and bindes agaist its plastic mating surface. When hauled out of the water its easy to acid clean the ball and its mating surface ...if the boats in the water its troublesome. Once cleaned there appears to be no lubricant or protection that can be applied to the ball.

    I suppose the lesson is that valves should be opened and closed regularly to scrape the ball surface clean. Kinda like everyone should brush and floss after every meal.

    Concerning unpolished stainless on a yacht. Since yachts are useless objects whose only mission in life is to look good , esthetics are important. Regulaly painted galvanized steel rails on fishing boats look better than rust bled stainless. I personally find aluminiun better looking than rusty stainless. Anodized aluminum looks very nice. And is durable. Anodized Aluminum is common on Italian motoryachts.
    The ultimate low maintance look is green tarnished bronze hardware
     

  11. pdwiley
    Joined: Jun 2008
    Posts: 1,004
    Likes: 86, Points: 48, Legacy Rep: 933
    Location: Hobart

    pdwiley Senior Member

    That's why I have bronze portholes. All I have to do is finish machining the things.....

    I'm going for the 'fishing boat' look with my build, not the 'pox doctor' look. Unpolished stainless is just fine with me.

    PDW
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.