Rust is a reaction to the air and moisture. Technically it is "iron oxide". And in the metals industry it is referred to as "oxidation". Many metals oxidize. Zinc and aluminum form a white powder when they oxidize. Iron forms rust. I think the correct metalurgical term is "form".
When we have parts tested in an accelerated test chamber (ASTM B117) we get reports that say "...96 hours to red rust..."