A METHOD FOR DEPOSITING A CHROMIUM OR CHROMIUM ALLOY LAYER AND PLATING APPARATUS

A method for depositing a chromium or chromium alloy layer on at least one substrate, the method comprising the steps(a) providing an aqueous deposition bath with a pH in the range from 4.1 to 6.9, the bath comprisingtrivalent chromium ions,formate ions, andoptionally sulfate ions,(b) providing the at least one substrate and at least one anode,(c) immersing the at least one substrate in the aqueous deposition bath and applying an electrical current such that the chromium or chromium alloy layer is deposited on the substrate, the substrate being the cathode,wherein, if during or after step (c) the trivalent chromium ions have a concentration below a target concentration of trivalent chromium ions, then(d) adding dissolved trivalent chromium formate to the aqueous deposition bath such that trivalent chromium ions are present in a higher concentration than before step (d),with the proviso thatsolid trivalent chromium formate is dissolved in a separated partial volume taken from the aqueous deposition bath to obtain said dissolved trivalent chromium formate for step (d).