US 12,359,331 B2
Method for electrodepositing a functional or decorative chromium layer from a trivalent chromium electrolyte
Jacques Hubert Olga Joseph Wijenberg, Amsterdam (NL); and Ganesan Palaniswamy, Haarlem (NL)
Assigned to TATA STEEL NEDERLAND TECHNOLOGY B.V., Velsen-Noord (NL)
Appl. No. 18/002,716
Filed by TATA STEEL NEDERLAND TECHNOLOGY B.V., Velsen-Noord (NL)
PCT Filed Jul. 15, 2021, PCT No. PCT/EP2021/069841
§ 371(c)(1), (2) Date Dec. 21, 2022,
PCT Pub. No. WO2022/013387, PCT Pub. Date Jan. 20, 2022.
Claims priority of application No. 20185961 (EP), filed on Jul. 15, 2020.
Prior Publication US 2023/0243057 A1, Aug. 3, 2023
Int. Cl. C25D 3/06 (2006.01); C25D 3/10 (2006.01); C25D 7/06 (2006.01); C25D 17/10 (2006.01); C25D 21/12 (2006.01)
CPC C25D 3/06 (2013.01) [C25D 3/10 (2013.01); C25D 7/0614 (2013.01); C25D 17/10 (2013.01); C25D 21/12 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A method for the electrodeposition of a functional or decorative chromium layer onto a metallic substrate in a batch or a continuous electrodeposition process from a halide-ion free and boric acid free aqueous electrolyte solution, the electrolyte comprising:
i) a trivalent chromium compound provided by a water-soluble chromium(III) salt wherein the electrolyte solution contains at least 50 mM and at most 1000 mM Cr3+-ions;
ii) a total amount of from 25 to 2800 mM of sodium sulphate or potassium sulphate;
iii) a formate salt as a complexing agent at a

OG Complex Work Unit Math
molar ratio of at least 1:1 and at most 4.0:1;
iv) optionally sulphuric acid or sodium hydroxide or potassium hydroxide to adjust the pH to the desired value;
v) optionally a surfactant to facilitate the release of hydrogen gas bubbles from the substrate,
wherein the aqueous electrolyte solution has a pH of between 1.50 and 3.00 measured at 25° C. and wherein the temperature of the aqueous electrolyte solution during electrodeposition is between 30 and 60° C., wherein the substrate acts as a cathode and wherein one or more anodes comprising a catalytic coating of i). iridium oxide or ii). a mixed metal oxide comprising iridium oxide and tantalum oxide for reducing or eliminating the oxidation of Cr3+-ions to Cr6+-ions, and wherein the electrodeposition is performed by means of pulsed electrodeposition comprising two or more current pulses at a selected current density for a selected pulse duration, wherein each current pulse is followed by an interpulse period wherein the current density is set to 0, wherein the interpulse period is at least 0.1 seconds and wherein the pulse duration is at least 0.1 seconds.