Patent ID: 8110087

Claim:
A method of producing a structured hard chromium layer, the method comprising: providing an electrolyte having a chemical composition comprising: (a) a Cr(VI) compound in an amount corresponding to 50 to 300 g/l of chromic acid anhydride; (b) 0.5 g/l to 10 g/l of sulfuric acid; and (c) 5 g/l to 15 g/l of aliphatic sulfonic acid comprising 1 to 6 carbon atoms; wherein the electrolyte comprises substantially none of the compounds selected from the group consisting of ammonium molybdate, alkali molybdate, alkaline earth molybdate, ammonium vanadate, alkali vanadate, alkaline earth vanadate, ammonium zirconate, alkali zirconate and alkaline earth zirconate; and wherein the electrolyte comprises substantially no fluorides; and electrodepositing chromium from the electrolyte onto a workpiece forming a structured hard chromium layer, wherein the structured hard chromium layer is electrodeposited at a temperature between 55° C. and 90° C. and a current density between 40 A/dm 2 and 200 A/dm 2 , and the chemical composition of the electrolyte, the temperature and the current density are selected such that a cathodic current yield of 12% or less is employed to form the structured hard chromium layer consisting essentially of at least one of a cup-shaped structure, a labyrinth structure, or a column-shaped structure.