CONTROLLED METHOD FOR DEPOSITING CHROMIUM OR CHROMIUM ALLOY LAYER ON AT LEAST ONE SUBSTRATE Russian patent published in 2021 - IPC C25D3/06 

FIELD: electroplating equipment.

SUBSTANCE: method includes stages of (a) providing an aqueous precipitation bath, wherein the bath contains trivalent chromium ions, bromide ions, alkali metal cations in the total amount from 0 mol/l to 1 mol/l per the total volume of the precipitation bath, and the bath has target pH in the range from 4.1 to 7.0, (b) providing the specified at least one substrate and at least one anode, (c) immersing the specified at least one substrate in the aqueous precipitation bath and supplying direct electric current so that a chromium or chromium alloy layer is deposited on substrate, which is cathode, wherein, during or after stage (c), pH of the precipitation bath is lower than target pH, (d) adding NH₄OH and/or NH₃ during or after stage (c) to the precipitation bath so that target pH of the precipitation bath is restored.

EFFECT: obtaining a chromium layer or a chromium alloy layer with average roughness of less than 0.5 mcm, excellent hardness and wear resistance during long-term operation of the precipitation bath.

15 cl, 2 dwg, 2 tbl, 2 ex