Originally Posted by sailboy21
While browsing the web for boat stuff (what else?) I ran across a fuel tank manufacturer that issued a warning not to use rubber in contact with aluminum. The reason stated, was rubber contains carbon which exists on the galvanic series, and is slightly more noble than passivated stainless steel.
I immediately thought of my stainless steel masthound for my inner forestay.
I had placed a rubber gasket to insulate the stainless from the aluminum. It had never occurred to me that I may have been creating a bigger galvanic cell! I removed the masthound and found zero evidence of corrosion after two years.
Has anyone heard of an issue with rubber against aluminum? I usually use HDPE as an insulating material, and religiously use tefgel on fasteners, but I had a sheet of generic black rubber gasket material handy at the time. Should I replace the rubber with a sheet of HDPE or leave it alone?
Certain rubber gaskets and shrouds do contain carbon... Carbon is actually a very good electrical conductor (Carbon Fiber for example is a great electrical conducer)..
So the marks are not that far off - you can minimize the effect / severely limit however... if you are attaching to another metal - lubricate it with silicon sealant which is not as conducive and will prevent contact of the two...If the boundary is there - due to the lower level in the rubber - you will be out of harms way....but it is not a myth it actually happens...