EvapoRust is your friend :-). Depending on size and weight, maybe put down a thick polyethylene dropcloth sheet on the floor, put a couple of bars down to hold the sheets 1/4" off the floor, then put a sheet down, prop the edges of the plastic up to form a pool, and pour in the evaporust so the metal is submerged. Put another plastic sheet over it to limit evaporation and go away for a day or three. Pick that sheet up, drain off all the evaporust you can, go wash that sheet and put in the next steel sheet. Will take some time but very little effort or labor. If you can arrange a "sump" to get the liquid deep enough in one spot, put in a little pump of some kind to keep the stuff flowing and it will work faster. Warm it up and it will work even faster - got any 500W halogen work lites? Just shine them on the rusty steel.
I have a bunch of street plate steel, that I want to magically transform into welding tables.
They have rust on them, it is not horribly deep, but it needs to be removed.
What is the most efficient way to do it using, say, a 9 inch angle grinder. What abrasive things are best for it?