Heating an aqueous mixture of a fluoroacid such as H2TiF6 and an oxide, hydroxide, and/or carbonate such as silica produces a clear mixture with long term stability against settling of any solid phase, even when the oxide, hydroxide, or carbonate phase before heating was a dispersed solid with sufficiently large particles to scatter light and make the mixture before heating cloudy. The clear mixture produced by heating can either be mixed with water soluble and/or water dispersible polymers, for example with dispersed polymers of the diglycidyl ether of bisphenol-A or an acrylic acid polymer, or with soluble hexavalent and/or trivalent chromium, to produce a composition that improves the corrosion resistance of metals treated with the composition, especially after subsequent painting. Another composition that improves the corrosion resistance of metals after contact with them is an aqueous solution of a mixture of: (A') a water soluble or dispersible polymer having at least one -OH group per polymer molecule selected from the group consisting of polyvinyl alcohol, polyethylene glycol, modified starch, and mixtures thereof, and (B') polymers and copolymers of acrylic and methacrylic acid and their salts.