Method for treatment of a chromium finish surface

A method for post-treatment of a chromium finish surface to improve corrosion resistance, comprising

• a) providing a substrate having a chromium finish surface, and at least one intermediate layer between the chromium finish surface and the substrate, wherein the at least one intermediate layer is selected from the group consisting of nickel, nickel alloys, copper and copper alloys, wherein the chromium finish surface is a surface of a trivalent chromium plated layer, obtained by electroplating the substrate having the at least one intermediate layer, in a plating bath, the plating bath comprising chromium (III) ions as a main chromium source;
• b) contacting the chromium finish surface with an aqueous solution, comprising
• a permanganate, and
• at least one compound which is selected from a phosphorus-oxygen compound, a hydroxide, a nitrate, a borate, boric acid, a silicate, or a mixture of two or more of these compounds;
• and
• c) forming a transparent corrosion protection layer onto the chromium finish surface during contacting the chromium surface with the aqueous solution in step b, wherein in step b) an electric potential is applied between the chromium finish surface and an inert counter electrode, wherein the chromium finish surface serves as a cathode and the inert counter electrode serves as an anode.