It has been discovered that contaminants such as metals and/or amines can be transferred from a hydrocarbon phase to a water phase in an emulsion breaking process by using a composition that contains water-soluble C5-C12 polyhydroxy carboxylic acids, ammonium salts thereof, alkali metal salts thereof, and mixtures of all of these. The composition may also optionally include a mineral acid to reduce the pH of the desalter wash water. The method permits transfer of metals and/or amines into the aqueous phase with little or no hydrocarbon phase under-carry into the aqueous phase. Resolving the emulsion into the hydrocarbon phase and the aqueous phase occurs in a refinery desalting process using electrostatic coalescence. The composition is particularly useful in treating crude oil emulsions, and in removing calcium and other metals therefrom. The polyhydroxy carboxylic acid additionally inhibits metal corrosion of metal pipe or other equipment used in a crude unit.