[TheForge] Pit cast iron (or steel?)

[Bruce Freeman]

A friend is working on an artistic casting, currently with a ground
surface.  He wants to "age" it by pitting and rusting.  He's tried
muriatic acid (at cold, outdoor temperatures) and it's a no-go so far.

I've advised him  NOT to move muriatic inside.  He's thinking about
other chemicals and could use some advice. Does anyone have practical
experience trying to accomplish such pitting, and can tell how?

-- 
Bruce
NJ