Calif Bill wrote:

Bare Alminum boats are acid washed at times to get them clean.

The material I quoted was from a university website, but that
disclosure got caught up in the post I was replying to. I think acid
might be OK, as the university site said to avoid the use of alkali.

With acid, I think there might be a concern about how the acid might
react with some of the crud stuck to the hull- rather than the aluminum
itself.......