Derivative…

https://www.warhol.org/conservation/oxidation-paintings/

Now THAT would be cool! Paint a oxidising agent on a metal sheet and wait. As the sheet continues to rust the piece evolves over it's lifetime.

I wonder how much variation you could get by using several oxidising agents of different strength?

Interesting project!

Richard Serra already did that, using massive blocks of self-oxidising steel so his sculptures "evolve" with time.