Muriatic acid is some bad **** to work with, plus if your using it in an area where other parts are bare metal, it will cause flash rust from its fumes. Better use some serious PPE in the form of gloves, eye protection, respirator etc. It is also hard to dispose of. Molasses and water mixture can be dumped in the ground, and doesnt require any special PPE. i suspect vinegar can be dumped in the ground too. Muriatic acid will continue to keep attacking the metal if you dont neutralize it good enough. My vote is for something that works a bit slower but is easier to work with, less hazardous.