Hexafluorozirconic acid is an inorganic compound with the chemical formula H<sub>2</sub>ZrF<sub>6</sub>. It is a white solid.
Hexafluorozirconic acid can be prepared by treating zirconium(IV) oxide with hydrofluoric acid. White crystals form upon evaporation of the solution.
Hexafluorozirconic acid can be used in sealing treatments for phosphated steel. A dilute solution of trimethoxymethylsilane, with enough H<sub>2</sub>ZrF<sub>6</sub> to bring the pH down to about 4, is reported to perform better than a chromate rinse. A nickel and chromium(VI) free treatment system for steel and galvanized steel is carried out by washing with an alkaline cleaner, rinsing, treating with hexaï¬Âuorozirconic acid, rinsing, and then sealing with a solution of epoxy phosphate.