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Bare Aluminum Structure? Why No Protective Coatings?

Discussion in 'Technical' started by James Anders, Apr 30, 2016.

  1. James Anders

    James Anders Member

    Mar 13, 2014
    Southampton, PA
    It seems to me that the chassis and much of the under-structure of Model S (and probably Model X) is bare aluminum with no protective coating.

    As a design engineer I've always seen and specified chromate conversion coatings (either a dip or spray) to reduce the possibility of corrosion and oxidation.

    Alodine or Iridite are two well known brands. Can either be clear or a yellowish-straw color.

    It's not very expensive and I wonder why (if I am correct) Tesla doesn't do this?
  2. wdolson

    wdolson Supporting Member

    Jul 24, 2015
    Clark Co, WA
    The sorts of alloys of aluminum used in aircraft are subject to corrosion and they are often coated with some kind of chromate to protect them, but pure aluminum is very corrosion resistant. It forms a layer of aluminum oxide and then quits corroding.

    During WW II the US developed alclad for aircraft. It's an aircraft aluminum allow that is coated with pure aluminum and it protects the metal quite well from corrosion. That's why most late WW II US aircraft were bare metal, not painting them saved time and weight.

    Alclad is still used on airliners built for airlines that use bare metal areas on their aircraft. American Airlines paints some of their aircraft now, but for many years left most areas of the plane in bare metal.

    I doubt Tesla is using anything as soft as pure aluminum for structural components of the car but they may be using an allow that doesn't corrode or alclad on a stronger alloy.
  3. jaguar36

    jaguar36 Active Member

    Apr 10, 2014
    I'll have to check when I get home, but I suspect that Tesla uses something like a clear chromic acid anodization on the aluminum parts. Its a pretty standard coating, and theoretically offers more corrosion protection than alodine.
  4. JeffC

    JeffC Member

    May 15, 2016
    Silicon Valley
    Yes. Some alloys of Aluminum form their own protective oxide layer, a bit like anodizing, and a bit like the corrosion protection mechanism of stainless steel or Titanium. (Actually more like Titanium than stainless steel since the latter is an alloy where chromium forms the oxide layer.)

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