Hi John,
> the lever. Using ammonia will most certainly discolour the
> aluminum and phosphoric acid will attack it.
I was told that Coca Cola is helpfull if it is a corrosion issue- it contains some phosphoric acid I guess. It's worth a try, as it probably will not destroy the color. The Coke (and the sugar) can be washed out with water later. Don't know if this works, I prefer brute force in most cases, with different and interesting results. Good luck!
best regards, Richard
Richard Timm,
Hamburg, Germany