Cleaning white residue from exterior of Genesis firebox

[MikeH_MKE]

So, what is this residue, and what cleans it off?
This is after 2 scrubs with mild soap. That helped some, but I don’t want to waste my time on something that would be easy with some specific cleaner. I’ve got it somewhere or other on all my aluminum gill boxes.
https://drive.google.com/file/d/1qTMJiC2OF-5qm8iHkWXs6xfaOABV5GvS/view?usp=drivesdk

 

[THyde]

It's aluminum oxide, the aluminum version of rust. Just sand it and repaint the firebox.

 

[Dan Leighton]

We went into a similar situation in the 1980's when our firetrucks went from steel bodies to aluminum. Steel rusts - Aluminum grows even under paint as it oxidizes.

 

[MikeH_MKE]

Thanks guys