EP3022337A1 — Method for cathodic corrosion protection of chromium surfaces

USPTO Abstract

The present invention concerns a method for cathodic corrosion protection of a substrate having a chromium surface and at least one intermediate layer between the substrate and the chromium surface, selected from the group comprising nickel, nickel alloys, copper and copper alloys and wherein said chromium surface is contacted with an aqueous solution comprising at least one compound containing phosphorous while passing an electrical current through said substrate, at least one anode and the aqueous solution wherein said substrate serves as the cathode. The phosphorous compound is preferably a phosphonic acid of type RR2R3P03, wherein R is selected from the group consisting of n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadexyl, n-heptadecyl, n-octadecyl, unsubstituted branched C8 to C18 alkyl residues, and wherein R2 and R3 are H or a suitable counter ion selected from Li+, Na+, K+ and NH4 +. The aqueous solution comprises also at least one additive which increases the solubility of the phosphonic acid.