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Plain steel fasteners on Roadster bottom pans = Galvanic Corrosion

Discussion in 'Roadster' started by ShawnA, Mar 5, 2018.

  1. ShawnA

    ShawnA Member

    Nov 13, 2017
    Edwardsburg, MI
    I was under the Roadster yesterday to program the rear antenna of the TPMS system.
    I had to remove the pan under the two blowers. My Roadster still has 2 motors on the fans.

    I was disappointed to see so many rusted fasteners on the undercarriage holding the various aluminum panels
    in place.
    Both the fasteners and the fender washers were badly rusted.
    I replaced the 4 plain steel bolts and washers with stainless steel.
    The screws were M6 x 1mm x 16 mm long.
    I was able to get a 5 pack of M6 x 1mm x 20 mm long and some stainless fender washers 1/4" hole x 1" OD
    at Lowes. The extra length did not cause any problems here.

    This worked well for the 4 screws that I removed and replaced.
    There are many more rusted fasteners.
    I have a box of M6 x 1mm x 16 mm long screws coming from McMaster.
    I will replace all of the plain steel screws and fender washers while I still can...

    There were additional fasteners on the pan that I believe were M4 with washers.
    Both the M4 size fasteners and their washers were stainless steel.

    My Roadster is not a high mileage car but it is exposed to rain and minerals from the roads here in the Midwest.

    I am spreading the word after reading of the galvanic corrosion on the Ecohitch and the power steering failures
    on the Model S related to galvanic corrosion...
    Unfortunately, we have it on the Roadster with the steel screws and washers in contact with the aluminum bottom pans.

    • Informative x 2
  2. ICON

    ICON Member

    Jan 31, 2015
    Hong Kong
    When I had the front bumper for a a fresh coat of paint it was a nightmare to try and get the rusted bolts and nuts off, the garage took one whole day to do this - they have all been replaced with the proper galvanized hardware.
    • Informative x 2
  3. Rolf68

    Rolf68 Member

    Jul 24, 2015
    That's right. A pity they didn't use stainless screws by default on such a car.

    I'll change them too as soon as I get the opportunity to go under the car.
  4. Stefan T

    Stefan T Member

    Jan 31, 2015
    I have swapped mine screws to Stainless Steel
  5. ThisoldRoadstr

    Mar 4, 2018
    This is the solution. Had same issue.
  6. hcsharp

    hcsharp Active Member

    Jun 7, 2011
    I've replaced most of the plain steel fasteners with SS. The only parts I haven't found a good replacement for are the clip nuts that many of the under-pan screws go into. I've replaced them all with black oxide but they really need to be stainless.
  7. RobertinWC

    RobertinWC New Member

    Mar 6, 2018
    Walnut Creek CA
    Hello all

    Just so you know, stainless fasteners on aluminium can still see galvanic corrosion. Stainless is also subject to crevice corrosion, which occurs when the stainless does not get exposed to oxygen, nuts and bolts, where the nut covers the bolt. The way to prevent either of these from occurring is to use a product called Lanocoat, which is lanolin based. It's very commonly used on sailboats and found in marine supply stores.

    Hope this helps
    • Informative x 1

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