A magical corrosion proof, marine growth proof, strong metal. What was it?

Discussion in 'Materials' started by Matthew777, May 16, 2020.

  1. gonzo
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    gonzo Senior Member

    Hydraulic oil will not stay adhered to a submerged surface in salt water for 40 years. Further, galvanic corrosion does not promote marine growth.
     
  2. Will Gilmore
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    Will Gilmore Senior Member

    By "it", I was actually referring to the chrome. Sorry for the ambiguity.

    I don't know what galvanic charged corrosion does to marine growth.

    -Will (Dragonfly)
     
  3. fallguy
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    fallguy Senior Member

    The reason no marine life attached to the struts is oil. Perhaps kerosene?

    The way a barnacle works is it displaces water from the surface by a droplet of oil that it can then glue itself to the underlying substrate. If you use an oil on the substrate that is not chemically compatible or even perhaps toxic to the critters; they either can't adhere (likely) or they die trying. The problem, of course, is we cannot coat everything with oils and if we could; it would require constant repeating. Most likely; the oils may have even seeped out of the strut for a long time as certainly some corrosion began. So, my hunch is that the real story is the thing was too oily or a special kind of oily for barnacles to latch onto.

    Perhaps our bottom paints need some magical oil in them. I suppose they would then be accused of pollution as they slough oil and kill fishes

    As for the metal itself; if you sampled everything under the sea; it does not simply rot everything to dust. But the critter growth makes everything look buried.

    ...my thoughts worth price charged...no idea about the metal

    weird thing about kerosene though is it is really light, so not sure if the currents would rwash it away quickly---one would think...maybe not kerosene

    After 150 Years, Scientists Finally Know How Barnacle Glue Works https://gizmodo.com/after-150-years-of-mystery-scientists-now-know-how-bar-1607232968
     
  4. Will Gilmore
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    Will Gilmore Senior Member

    I'm sort of leading a review of Collier's book: Boat Owner's Guide to Corrosion, on the sailboatowners forum. I don't know much about the subject, so it's kind of funny that I should be the lead on this subject, but it is fascinating and We are learning a lot. Here's a link to a post where I talk about Collier's section on protective coatings. He mentions Cosmoline, an oils-based coating used since the Civil War.
    Sailboat Owner's Guide to Corrosion - Protection (Collier 13 - 15) https://forums.sailboatowners.com/threads/sailboat-owners-guide-to-corrosion-protection-collier-13-15.1249923256/post-1624418

    -Will (Dragonfly)
     
  5. fallguy
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    fallguy Senior Member

    I bought a Korean War stove built in 1953 maybe 4-5 years ago. It was coated in cosmoline; had nearly no rust on it.. I tried to sell it; no takers, burned the cosmo off and it rusted real bad after that. Stuff is weird.
     
  6. David Jones
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    David Jones Junior Member

    WWII hydraulic rams were typically chromium hard coat plated. Not a decorative type coating, but a functional coating. The functional coating would likely not have the cracks or holidays (small pin holes) as suggested earlier. One would have to do an evaluation of exactly how they did the coating in the specific case being discussed, however, generally for hydraulic ram coatings, they would be extremely smooth, hard and very corrosion resistant. Longevity in the environment as described by the OP could be significant. There are lots of variables one would have to consider, but really, it's not surprising to hear the observed lack of corrosion and lack of biofilm.

    Decorative Cr coatings are not the same thing, most of the above discussions I've read through pertain more to those then high performance chromium hard coats.

    for what it's worth...

    dj
     
  7. gonzo
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    gonzo Senior Member

    The only difference between hard chroming and decorative chroming is the thickness of the plating. It would not make any difference on marine growth. However, chromed metals get marine growth, which would point to cupro-nickel alloys.
     
  8. David Jones
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    David Jones Junior Member

    That is not the case. Read AMS 2460 - it provides some basis in their differences.

    In addition, we don't know what they did in the manufacture of the parts in question, they may have done pre or post processing on the coating to decrease roughness.

    I guess they could have gone to a cupro-nickel alloy, but for a hydraulic cylinder, I see no design reason to do so. They weren't planning on reducing marine growth on an airplane component. All rational design constraints on a hydraulic cylinder on an airplane point to lower weight and higher strength, that would not be a cupro-nickel alloy.

    dj
     
  9. David Jones
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    David Jones Junior Member

    Another thing to point out. the OP said it was stainless steel, but that may well not be the case. It very well could be chromium on top of aluminum. They may have used hexavalent chromium coating on a high strength aluminum - I don't know if that combination was used in landing gear and I don't know how that resists marine growth, but hexavalent chromium is not friendly to biological organisms... Just a thought...

    dj
     
  10. gonzo
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    gonzo Senior Member

    Please quote the standards. Your link costs $85.00 to read.
     
  11. gonzo
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    gonzo Senior Member

    Considering the age it would be hexavalent chromium in the solution to plate any parts. The only difference with trivalent chromium is the color consistency of the finish. Chroming aluminum, even if possible, would not be part of a landing gear. Seems like you are using polysyllabic words to try to make an impression. In fact chromed finishes are very environmentally friendly since they don't easily corrode or dissolve.
     
  12. David Jones
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    David Jones Junior Member

    Apologies just saw this.

    I can quote some parts I guess, but i'm not sure how much is permitted by copyright laws. Here's what is says about class 1 chromium coatings:

    8.4.3 Class 1 Chromium Plating
    8.4.3.1 The function of the under layer of nickel for Class 1 plating is to provide a pore free continuous underplate for
    the chromium outer layer. Generally, the thicker the nickel layer, the better the corrosion resistance. The system
    of an outer layer of chromium over the combined plated nickel and copper are generally used in a combined
    total thickness of 0.0001 to 0.002 inches (2.5 to 51 m) depending upon service conditions and the basis metal.

    Here's what it says about class 2 coatings:

    8.4.4 Class 2 Chromium Plating
    8.4.4.1 Class 2 plating, also known as “engineering chromium”, “industrial chromium”, or “hard chromium” is typically
    used for wear resistance, abrasion resistance, improved frictional properties (lower), and such incidental
    corrosion barrier protection of parts as the specified thickness of the plating may afford. Class 2 plating is
    usually applied directly to the basis metal and is finished by grinding to the specified dimensions. It lacks the
    brightness of Class 1 plating. Additional corrosion resistance can be obtained by use of an undercoat of
    electrodeposited nickel in thickness of 0.001 to 0.002 inch (25 to 51 m) on ferrous parts, the minimum
    thickness to be determined by service conditions. Heavy deposits of the Class 2 plating have been used for
    buildup of worn or undersized parts, or for salvage purposes, and to provide protection against corrosive
    chemical environments. Final grinding of the chromium plating can increase the incidence of cracking in the
    deposit. For greater corrosion resistance, based upon equal thickness, unground deposits should be selected
    rather than ground deposits. See 8.4.4.4. A reduction in fatigue life of chromium plated parts can be expected
    and is attributed to the physical and adhesion characteristics of the chromium plate and its state of stress.
    Plating bath temperature and embrittlement relief (baking) temperature have been found to affect the fatigue
    performance of Class 2 plating.

    So there are substantive differences in chromium coatings, and I'm only citing one specific chromium coating specification. there are numerous, and I don't know what they would have been using at the time this particular landing gear was made.

    dj
     
  13. David Jones
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    David Jones Junior Member

    sigh....

    upload_2020-5-28_16-43-59.png
     
  14. gonzo
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    gonzo Senior Member

    I'm not sure what point you are trying to make or refute.
     

  15. gonzo
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    gonzo Senior Member

    In short, that is what I was saying. The significant difference between the hard and cosmetic chroming is the thickness.
     
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