We use similar stuff at my work. As I work on ships and barges, everything get rusty, from forklifts to frontend loaders. I use that stuff with alot of small components that are too small to sand blast. I've got a 302 Mexican block that I might use it on. I dilute the stuff at my work 4:1 (4 parts water and 1 part dissolver) and it still works a treat.
Hopefully it won't dissolve the Mexican block! Haha