I like using AAI Industry in Vanilla+ games, and blasting the rust off the iron parts with Sand from AAI Industry would make a lot of thematic sense, imho! And AAI Industry early-game is painful, so I think being unable to de-rust until you can make sand would fit the difficulty curve.

Bonus idea: Engine units rusting would also make sense, since they're entirely made of iron, and could take twice as many resources to de-rust? Maybe as an optional setting, since that would make crafting blue science harder.

Your note about engines is well-taken, that's the logical next step. It's added to this mod as a setting, on by default.

Per your advice, when AAI Industry is enabled the sandblasting material is changed to sand (and the single-cylinder engine rusts.)

Hell yeah, thanks for the quick turnaround and glad you liked the idea