Depends on what you mean by corrosive. It will not cause corrosion to a structure it is applied to. Aluminum does corrode, but the oxide is relatively transparent. As it corrodes and the thickness of the corrosion builds up, it will lose a bit of sheen. I am assuming the vehicle of Alclad greatly slows corrosion, but even if it does corrode, since any but the polished aluminum is already a bit dull, I would assume it would be many years before you'd notice any change in gloss on those. I suspect the polished aluminum, if applied over a really good base to give it a highly polished look, might eventually loose some gloss. But I have some really shiny planes with a very polished look with polished aluminum that are about seven years old, and they are as shiny as the day I finished them.