I blast at 40psi using Black Beauty and a 2 sq/in section would take about 20 seconds. Unless the OP meant 2sq/ft High pressure just shatters the media faster making dust - "2x2 in sq."
Al oxide really isn't the right media for rust... paint only, yes. Surface rust, getting iffy.
50lbs of Black beauty is $8.. change it when it slows down.
I use 1/8th in ceremic tips. At the low pressure I run they are good for a few hours. I would go carbide if I did blasting for a living, but just for one or two trucks ceremic will be fine.
