Abstract: Solution and procedure for depositing a coating, comprising hydrated zinc pyrophosphate, on the surfaces of galvanized steel parts, to protect against corrosion in the presence of water. The aqueous solution contains, per liter of final solution, hexametaphosphate equivalent to 10 to 70 grams of sodium hexametaphosphate, metasilicate equivalent to 1 to 40 grams of sodium metasilicate, an amount of orthophosphoric acid equivalent to 15 to 40 milliliters of orthophosphoric acid having a density of 1.71 g/ml, zinc chloride in an amount equivalent to 10 to 50 grams of anhydrous zinc chloride, and calcium carbonate sufficient to bring the pH of the solution to between 2.0 and 3.0. Nickel, equivalent to 0.5 to 20 grams per liter of final solution of hexahydrated nickel chloride, and chlorate, equivalent to up to 20 grams of sodium chlorate per liter, may be added. The solution is used by contacting it with the parts to be treated for a time determined on the one hand by the solution temperature (between 10.degree.