Originally Posted by Deejay
Originally Posted by Rog
Swapping silencers around today to try and locate something loose in the exhaust. Whilst the exhaust was off I took the opportunity to replace the five steel screws directly below the door that holds the wing to the body with aluminum screws. I’m guessing but these steel screws might be responsible for the bimetallic corrosion that causes the bodywork to bubble just below the doors? I’ve seen this on a few cars. Any water or screen wash run off may run past the wing beading into the joint. I replaced the screws on the other side a while back and those screws were more rusty compared to this hot exhaust side. Anyway no bubbling so far so far, fingers crossed this might prevent it smile

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[Linked Image]
I am a little wary of aluminium screws! When i renewed the guttering on the house, I used ali screws on the down pipe clamps to prevent eventual rust marks staining down the wall. However, when I needed to remove them, the heads turned to powder and were devils to get out. Maybe salt air as we are only a couple of miles from the coast, though the Severn is more mud than salt!

Doug I would guess that the demise of your gutter screws may have been from atmospheric corrosion unless the gutters were steel? Hopefully these screw heads will be protected to some extent from the atmosphere with a few coats of Dinitrol. That’s not my concern here. My concern is the long term galvanic corrosion between the dissimilar metals where the steel screws pass through the aluminium body skin and then fueled with a regular dowsing of electrolyte that manages to gets past the wing beading.

If you look closely at the original screw the most corrosion has occured at the neck just below the head where moisture has run down the screw (the external portion is not corroded). When I took the screws out on the N/S they were even more corroded. One of those five annoyingly completely sheared off owing to the rust at the neck. So like the steel screws the worst that can happen is the ali screws also shear but at least the risk of any bodywork bubbling might be reduced with the similar materials, that’s my rational…. smile

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Roger
2011 Plus 4