Concerns over mixing aluminum and stainless steal

Discussion in 'Apple Watch' started by TRICKorDEVICE, Mar 24, 2015.

  1. TRICKorDEVICE, Mar 24, 2015
    Last edited: Mar 24, 2015

    TRICKorDEVICE macrumors 6502a

    Sep 20, 2014
    For those of you concerned with the look of mixing stainless steel and aluminum. Or of the chemical reactions. Apple has done this before. The Apple logo on the iPhone 6 says hello. If memory serves me correctly the Apple logo on the back of every iPhone six is stainless steel.


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  2. JayLenochiniMac macrumors G5

    Nov 7, 2007
    New Sanfrakota
    Except people don't typically leave iPhones out in marine environment or subject it to salt (sweat) by wearing it on the skin.


    "Aluminium and stainless steel together also appears to be a bi-metallic corrosion risk, from the 'nobility' table. With this combination the affect of relative surface area on corrosion is important.

    A large area of 'cathode' relative to 'anode' will accelerate the anodic corrosion. Although aluminium is anodic to stainless steel, large relative surface areas of aluminium to stainless steel can be acceptable, dependant on local conditions. Stainless steel fasteners in aluminium plates or sheets are normally considered safe, whereas aluminium rivets or bolts holding stainless steel parts together is an unwise combination, as there is a practical risk of corrosion.

    An example of the safe use of stainless steel and aluminium together is where stainless steel fasteners and hold down bolts are used to secure aluminium roadway or bridge parapet guards. Even with no insulation between the metals, there should be little risk of corrosion.

    In contrast, in a marine environment, severe localised pitting corrosion to the aluminium treads has been observed where un-insulated stainless steel bolts were used to secure the treads in place. On the same ladder however, bolts with sound insulating washers did not show any pitting on the surrounding aluminum.

    Based on this, a small stainless steel connector to a large aluminum body would normally not pose a problem. However, the presence of sweat (from working out or just from wearing the watch on a hot day) may change this equation.

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