I work with HF, It is friggin nasty shit, but Alien blood it is not.
Hydrofluoric Acid is ridiculously corrosive to organics and metals, but is considered a 'weak acid' due to its low dissociation constant.
Essentially it penetrates skin and flesh, strips calcium from the bones then works it way back. If you've watched Breaking Bad season 1 where they dissolve the body in a bathtub slowly over a week until its a goopy liquid mess.....HF.
Wipe or wash it off and it keeps burning!! Calcium Gluconate is needed to stop the reaction. Nasty, nasty shit!!
Hydrofluoric Acid also attacks silicates, which seems to go against the chitinous exoskeleton of the Xenos.
Science Bitches!