Originally Posted by JoeBoxer

Idealy, you would have a carbon seat post, to prevent galvanic corrosion. In your situation, the aluminum will corrode because it is the anode with a potential of -1.67, and the carbon the cathode with a potential of +0.81. A difference in potential of 2.48 volts. Where as titanium and carbon both have + potential, and the resulting difference is only 0.755 volts, which is negligible. (Remember kids, that even though both carbon and titanium are both + charges, its the difference in potential that creates a charge.

To reduce or prevent the effects of galvanic corrosion, you can simply get the aluminum seat post anodized, which would give it a non-conductive coat to it. Or a very fine rubber wrap would do just as well.

Don't be fooled by the black color, or that carbon isn't a metal. Carbon is highly conductive.