A SS304 plate with a thickness of 2 mm was used for the BPPs. The stainless steel was a commercially available product and the composition of the steel is shown in Table 1. The stainless steel plates were cut into sheets of 50 mm × 50 mm, polished with 2000-grit silicon-carbide abrasive paper, degreased with acetone for 2 min, activated using a 3% NaOH aqueous solution for 30 s and pickled in a 10% hydrochloric acid solution for 2.5 min prior to electroplating the trivalent Cr–C