Muriatic acid (HCL) is much safer and easier to get at any hardware store. Mix it 50/50 with water and immerse the degreased parts until clean. After cleaning, rinse the parts well with baking soda/ water solution to neutralize acid. Apply WD-40 or some other water displacer immediately as the metal is chemically clean and will rust in a heartbeat.
OB
I'm with OB, Muratic Acid (swimming pool acid) will clean the parts like new....any crustation or oxide will be removed A.S.A.P.....use heavy nylon fishing line to submerge each part, then dip immediately into a fresh water pail/bucket....inspect and re-dip as needed.........then as OB said, oil immediately.....
I use it at 75 acid- 25 water- (sometimes at 100% acid) and have had great results with all kinds of metal parts, guns, airplanes, engines and so forth.....you must stand over the process as the time submerged must be watched........don't run off to answer the phone..........
Do this process outside and do not breath the fumes.........common sense rules here.......and have a water hose running slowly along side this process.......