Galvanic corrosion happens when two dissimilar metals are in contact w/ one another in the presence of an electrolyte (such as salt water). There's no need to apply an external charge.
It's true that millions use alu posts in steel frames. That's good. It's also true that they will seize if you're inattentive (I recently had to use an old MTB handlebar as a pry bar to get one free in fact). That's bad.
Ah well, give it a shot. See if the stem corrodes away or fuses to your bars. Then you'll have your answer. We'll expect a full report.