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Rust

Discussion in 'TSLA Investor Discussions' started by marvinat0rz, May 10, 2013.

  1. marvinat0rz

    marvinat0rz Member

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    Hi guys. Long-term Tesla investor here, been reading this forum for a while. After the last month's crazy bull run, I thought it was time to see whether anyone has any input on a question that's been bothering me. I'm thinking about the deprecation and repair costs of Tesla's vehicles.

    I live in Norway, which is famous for its harsh winters and also for being Tesla's biggest foreign market. The killer of cars in this climate is invariably rust. During the winter season, the roads are salted with calcium chloride in order to lower the freezing point of snow and reduce the burden on the snow plowing crews. This is a long-standing tradition over all of Northern Europe, and it is not going away for a Californian carmaker. The salted roads cause a continous spray of salt water on the car, which produces one of the harshest climates for on-shore metal machinery in the world.

    Foreign carmakers have stepped in this trap multiple times. Toyota was at one point (during the 80s) notorious for making cars that rusted to death after two winters. Many of the smaller carmakers from Southern Europe are also known for these problems. Most other manufacturers have since then caught up. As another example, the intercity rail in Oslo has recently discovered that all of their trains have lethal rust problems and need to be replaced. The trains are made in Italy.

    So my question is, has Tesla thought about these issues? Tesla is a California-based carmaker which intends to sell globally. I am aware that Tesla have been doing cold-weather testing, but testing the handling and performance of your car in cold weather is not the same as subjecting it to three winters of negative (Farenheit) temperatures where the underside is sprayed with jets of salt water every time you drive. This is something that can only be simulated, not tested by taking a drive up to Canada.

    I am especially concerned when I look at the battery pack, which appears to be made of steel and is mounted underneath the car. If this rusts, it isn't merely an inconvenience that will deprecate the value of the vehicle - it is a safety risk that could necessitate a recall, which we all know could be disastrous at this point in Tesla's history. (Also, Norwegian law would require Tesla to pay for all repairs during the first five years after purchase, so any losses due to rust would be carried by the investors).

    So that was a bit of worst-case scenario thinking. I don't have any opinion as to whether Tesla has thought about these concerns during engineering, but I hope they have since they employ a lot of experienced automotive engineers.

    The big question: Can anyone allay my fears?
     
  2. spleen

    spleen Active Member

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    Isn't the body / battery casing made out of aluminum?
     
  3. yngwie_2012

    yngwie_2012 Member

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    Yea, the Model S is mostly of aluminum parts. And as we all know, aluminum is very good against rust. Its even better than galvanized zink coating which many german premium car makers use.
     
  4. marvinat0rz

    marvinat0rz Member

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    All right, that is a very relevant piece of information. Thanks.

    Aluminium doesn't rust the way iron does, but it does corrode. Aluminium corrodes to aluminium oxide, which doesn't flake off the way iron oxides do and hence forms a protective layer against additional corrosion. The behavior or aluminium in a wet and salty environment is different than that of iron/steel, but it appears that overall, it is more resistant to corrosion.

    See Aluminiums corrosion resistance - Aluminium Design for more information on aluminium and corrisoion. I thought from my chemistry classes that salts dissolve the layer of aluminium oxide, accelerating corrosion. But the aluminiumdesign link seems to indicate that this is only a cosmetic problem and not a structural issue.

    See Underbelly protection from salt | Forums | Tesla Motors and Corrosion engineering - Aluminum parts in cars getting corroded? for earlier discussion of corrosion due to road salt. A separate problem from corrosion due to water/chlorine ions is galvanic corrosion, which occurs when aluminium and steel parts are adjacent. But this is a problem that's obvious enough that Tesla's engineers must surely have thought of it.
     
  5. Cattledog

    Cattledog Active Member

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    Not a metallurgist, but the main issue with aluminum would be oxidation, not rust as it has nor ferrous content. I don't know what the fasterners are fabricated from that make the attachments. The oxidation would leave scaling and surface imperfections, but I seriously doubt failure issues.
     
  6. akula

    akula Member

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    The battery case is steel, not aluminum.
     
  7. vgrinshpun

    vgrinshpun Active Member

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    #7 vgrinshpun, May 10, 2013
    Last edited: May 10, 2013
    I have been told at Tesla store that battery casing is made of aluminum, but structural side beams attached to the casing are made of steel. I am not a corrosion expert by any means, but it is known that dissimilar metals theoretically are subject to galvanic corrosion. This is a valid question and I would not dismiss it without having in-depth knowledge on the subject.

    Having said that, I am an engineer by trade and did pretty thorough research on Tesla prior to investing. I was very impressed with evidence on their rigorous engineering, decision making and testing. It would be very surprising if they did not address the corrosion issue. Keep in mind that although the company located in California, their cars are shipped all over North America, which has plenty of regions with extensive use of salt during the winter.

    Just to offer an additional information to make you more comfortable with level of testing done at Tesla, its chief technical officer, JB Straubel indicated that in creating testing program Tesla took lessons from their partner Daimler, known in the industry for their rigorous testing:

    http://ev.sae.org/article/11923
     
  8. aznt1217

    aznt1217 Active Member

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    I would send an email straight to Tesla and find out directly if you are really that worried. I'm sure they've taken this into account (cold weather testing + salt spray-- they are in California) and all. But I am failing to see how this would be different from any other car. Aside from that I'm also sure that this problem can be solved in a modular fashion (some kind of enamel coating or vinyl even) to protect the bottom-- which is possible because you don't have gas heating up steel parts like a muffler, etc.

    You also have to remember that the battery is warrantied unconditionally, so you'd be fine
     
  9. deonb

    deonb Active Member

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    I believe marvinat0rz was asking from an investor perspective. Not a car-owner.
     
  10. kvietor

    kvietor Model S S280 VIN 168

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    It's amazing what you can learn using a simple magnet. Yes, battery case is aluminum and the rails are steel.
     
  11. bonnie

    bonnie Oil is for sissies.

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    Oh there you go, ruining all the discussion with facts :). Well done.
     
  12. kvietor

    kvietor Model S S280 VIN 168

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    Had time to kill while waiting for the market to open. Got my 3 year old grandson to crawl under the car and play with a horseshoe magnet. This is what my life has come down to in retirement. :biggrin:
     
  13. aznt1217

    aznt1217 Active Member

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    Haha I see, I was wondering if it was in the wrong thread. Apologies, but from an investor perspective... The roadsters have been on the road there for a while... Pretty sure Tesla got feedback about this stuff.
     
  14. Rarity

    Rarity Member

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    The first of SpaceX's rocket launches was doomed because of galvanic corrosion, as the rocket sat ocean-side.

    You can be sure that Musk is well aware of this issue.
     
  15. AWDtsla

    AWDtsla Active Member

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    Aluminum does not rust. Did we all miss high school chemistry? I doubt you will find a car in existence that is more corrosion resistant than a Model S, well other than a million dollar supercar made out carbon fibre and titanium.

    Open the hood of any modern car and you will see BARE aluminum exposed to the elements.

    Tesla is underselling this car.
     
  16. Doug_G

    Doug_G Lead Moderator

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    Steel rusts rapidly because the oxide is a catalyst. Aluminum does not because the oxide impedes corrosion. However, the presence of salt can accelerate corrosion... and guess what they like to ladle on the roads around here in winter...
     
  17. DrDave

    DrDave Member

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    I wish they would put e-coat on the body/battery packs, that would be the best way to prevent oxidation/corrosion. I wonder what that greenish/brownish coloration the battery packs have on them is?
     
  18. AWDtsla

    AWDtsla Active Member

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    Utterly pointless. Steel is coated with zinc because zinc oxidizes in the same way as aluminum. The only thing to "e-coat" it with would be GOLD.

    The car already has paint on it. Spray some paint on the bare aluminum suspension parts if you want it will keep it looking pretty longer, but it will never rust through like steel unless you send it to the bottom of the ocean and wait a hundred years.

    This thread is like a bad sci-fi movie. You know it's so so wrong. No, those oil miners aren't going to save the planet from the giant asteroid...
     
  19. Doug_G

    Doug_G Lead Moderator

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    Gold won't survive salt, either. It's why car manufacturers don't use gold plated connectors, even though they're commonly used for anti-corrosion purposes.
     
  20. DrDave

    DrDave Member

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    You haven't really been around auto manufacturing have you? Might want to check up on some links about ecoat technology in the industry and the benefits against corrosion protection, here are a few. I included all three major suppliers of ecoat for the automotive industry, DuPont, PPG and BASF. The ecoat is used in conjunction with a zinc-phosphate pre-treat system in most places, but others use a nano-treatment like Chemetall's Oxsilan .

    Electrocoat or E-Coat Metal Finishing Coating Technology
    DuPont E coat coatings
    Why Choose Ecoat? - Electrocoat

    http://www.basf.com/group/corporate/en/brand/CATHOGUARD_580
    Chemetall’s OXSILAN® Pretreatment Provides Significant Energy Savings | Cision Wire


    Tesla uses ecoat, FYI. My sarcasm above was obviously missed, I will use emoticons next time.
     

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