Disclosed herein are methods for preparing fluorided solid oxides by contacting an acidic fluorine-containing compound with an inorganic base to form an aqueous mixture having a pH of at least 4, followed by contacting a solid oxide with the aqueous mixture to produce the fluorided solid oxide. Also disclosed are methods for preparing fluorided solid oxides by contacting an acidic fluorine-containing compound with a solid oxide to produce a mixture, followed by contacting the mixture with a inorganic base to produce the fluorided solid oxide at a pH of at least about 4. The fluorided solid oxide can be used as an activator component in a catalyst system for the polymerization of olefins.