Hydrofluosilicic acid is also referred to as hexafluorosilicic acid, fluosilicic acid, and hydrogen hexafluorosilicate. This is a highly corrosive and toxic chemical compound that is commonly used for fluoridation of municipal water supplies. Aside from its use in water fluoridation, hydrofluosilicic acid is also used as an etchant in the semiconductor industry and as an ingredient in the production of aluminum. The acid is also used as a rust converter and as a concrete hardener. Despite its widespread use, hydrofluosilicic acid is considered a hazardous substance and should always be handled with caution.