Several decades ago, when I was studying various dug excavated war artillery metal sabots, and excavated Pewter, Brittania-metal, and "white tombac" buttons, I realized it is often (though not always) possible to figure out a metal's identity by the characteristics of the oxidation/corrosion on it.
Explaining what I mean by oxidation/corrosion characteristics:
The corrosion's "form" refers to characteristics such as powderiness, or crater-pitting, or cracks, or plate-like scaling, etc.
The oxidation's color is a clue to the metal's identity.
Keith351's pot shows the distinctive characteristics of Aluminum oxidation/corrosion ...so in my opinion, that's what his pot is made of.