Perchloric acid, a superacid, is one of the strongest Brønsted-Lowry acids. Its pKa is −10.[10] It provides strong acidity with minimal interference because perchlorate is weakly nucleophilic (explaining the high acidity of HClO4). Other acids of noncoordinating anions, such as fluoroboric acid and hexafluorophosphoric acid are susceptible to hydrolysis, whereas perchloric acid is not. Despite hazards associated with the explosiveness of its salts, the acid is often preferred in certain syntheses.[11] For similar reasons, it is a useful eluent in ion-exchange chromatography.
It is also used for electropolishing/etching of aluminum, molybdenum, and other metals. it is use in tbn mesurment