The present invention relates to a method for electrolytic passivation of an outermost chromium or outermost chromium alloy layer to increase the corrosion resistance of the outermost chromium or outermost chromium alloy layer, comprising: (i) providing a substrate comprising the outermost chromium or outermost chromium alloy layer, (ii) providing or preparing an aqueous, acid passivating solution comprising: Trivalent chromium ions, Phosphate ions, One or more organic acid residual anions, (iii) contacting the substrate with a passivating solution and passing a current between the substrate as an anode and a cathode in the passivating solution so that the passivating layer is deposited on the outermost layer, Wherein in the passivating solution, the trivalent chromium ions are obtained by chemically reducing hexavalent chromium in the presence of phosphoric acid through at least one reducing agent selected from the group consisting of hydrogen peroxide and an organic reducing agent, Provided that during or after chemical reduction, at least one organic acid residual anion is first present in the passivating solution.
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