The present invention relates to a method for electrolytically passivating an outermost chromium or outermost chromium alloy layer to increase corrosion resistance thereof, the method comprising the steps of: (i) providing a substrate comprising said outermost chromium or outermost chromium alloy layer, (ii) providing or manufacturing an aqueous, acidic passivation solution, the solution comprising: - trivalent chromium ions, - phosphate ions, - one or more than one organic acid residue anion, (iii) contacting the substrate with the passivation solution and passing an electrical current between the substrate as a cathode and an anode in the passivation solution such that a passivation layer is deposited onto the outermost layer, wherein in the passivation solution said 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 organic reducing agents, with the proviso that during or after the chemical reducing the one or more than one organic acid residue anion is present for the first time in the passivation solution.
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