Chris Lewis wrote:
According to PipeDown :
Sodium Hydroxide to be specific but unless there is just a thin film of
Aluminum, nothing is going to etch Al at any rate that is useful (at room
temp). If there are large chunks, it should not have alloyed with the steel
and should just chip right off. Smaller spatters might be removed with a
scotch brite cleaning pad.

It wouldn't have alloyed. Just stuck on. Rather like the way aluminum
fouls up abrasives (like grinding wheels). The way to get it off is
to chip/abrade it.

Seriously, the poster that suggested a torch is probably right on, the
melting point of aluminum is far lower than steel. Heat it just short of
cherry red and bang it on the ground or scrape with wire brush.

A torch is likely to deharden the shaft. You don't want to deharden
it any more than the sticking on of the aluminum already did.

I'd try various things like emory paper, a wire brush or a metal
scraper. Or even a fine file lightly wielded.

The shaft may be scored.

In some cases, you may need to take it to a machine shop (eg: some
automotive engine repair places) to have it touched up on a lathe.

Actually, that's what I was thinking. just on general principles, get a
competent machine shop to just true it up. Assuming that car crankshaft
machinery will work on this small stuff.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.