Hydrochloric acid is a chemical sample found in Cambridge Polymer Labs, initially found as unidentified sample 11317. Once the sample has been loaded into one of the polymer coating applicator's sample to holder, the option 'scan loaded reagents' needs to be selected from its terminal in order to identify the sample by its chemical name.
Other than when placed in the polymer coating applicator, hydrocloric acid cannot be removed from the player character's inventory.
Hydrochloric acid can only be found in Cambridge Polymer Labs. It can be found on the console desk next to the polymer coating applicator's terminal.