Aluminum against inside of door ok? - Alfa Romeo Bulletin Board & Forums
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post #1 of 5 (permalink) Old 03-31-2017, 10:14 AM Thread Starter
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Aluminum against inside of door ok?

I'm changing out the modern mirrors that were on my Spider for original style round mirrors. When the previous mirror was installed, large plastic inserts sort of like drywall anchors were used, so I have 5/16" holes where the original holes were. Looking at some other threads on the Board, looks like Alfa originally used a backing bar with in tapped hole on each end to receive the mirror screws and one in the middle that is attached to the door skin and holds the bar in place. I figured I probably make some backing bars since I won't need to pull the door apart in the future if I need to remove the mirror.

Anyway, to make my life easier, I was hoping to use 1/4" aluminum bar since it's a lot easier to work with than steel. Once installed, the bar pushes up against the inside of the door. Could this cause corrosion in the door? May just be overthinking it. Thanks for the help.
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post #2 of 5 (permalink) Old 03-31-2017, 10:43 AM
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In theory there could be some galvanic reaction between the two metals. As long as it stays dry I think the risk is minimal. You could separate/insulate the two with a piece of electrical tape or even a couple of coats of paint.
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post #3 of 5 (permalink) Old 03-31-2017, 11:11 AM
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It should be fine. Looking at galvanic corrosion tables there's only 0.1V potential difference between aluminum and steel with isn't much. And the aluminum has more corrosion potential, so if anything the aluminum will corrode and protect the steel.

I mean, the engine's aluminum and steel and it's perfectly fine.
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post #4 of 5 (permalink) Old 03-31-2017, 01:27 PM
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pic of original original backing plate

http://www.alfabb.com/bb/forums/7408089-post11.html

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #5 of 5 (permalink) Old 04-02-2017, 06:37 PM Thread Starter
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Thanks for the advice. I'll probably go ahead and shoot a couple of coats of paint on just to be on the safe side.

@spiderserie4 -- that's it. that's the backing plate I mean. Thanks
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