I've got several long sticks of 1/8" perforated angle that has been standing in a field for 20 years. I don't have a vessel long enough for a submerged soak, what is my second/third/fourth option?

Well, this forum sucks.

Thanks though to you Aero....

What is your intended end use for the perforated angle? The PVC pipe / Molases may work but the effort may not be worth the replacement $

Wire wheel? Sandblast? HF flap wheel finisher…, lightly rusted -paint on some ospho it’s phosphoric acid changes the iron oxide to iron phosphate.. then lightly wire brush and prime paint.  Got a pressure washer get the siphon sand blast attachment and water sandblast it just got to hurry and get it dry and painted.
Never heard of using molasses?? Sounds like a sticky mess.. but I am always willing to learn something new????

Have an air compressor?
HarborFreight portable sand blasters