Effects of Insoluble Anode on Deposition Behavior and Corrosion Resistance of Zn-Ni-SiO2 Composite Electroplating from a Sulfate Bath

Zinc-nickel-SiO2 electrodeposition was done using an acid sulfate bath to examine the effects of an insoluble anode on SiO2 co-deposition behavior and the corrosion resistance of plating. The presence of SiO2 nanoparticles in the plating bath apparently changes the alloy deposition behavior and improves the macrothrowing power of plating. At an early stage of electrodeposition, the SiO2 nanoparticle apparently acts as a nucleus of precipitation. The SiO2 amount co-deposited in the plating film by the iridium oxide electrode was greater than that by the platinum electrode. Furthermore, these SiO2 nanoparticles did not disperse uniformly in a plating film, but instead distributed only in the SiO2 rich layer formed beneath the surface. Therefore, the anticorrosive performance of the plating film with much SiO2 co-deposited amount by the iridium oxide electrode was superior to that obtained using a platinum electrode. For the curtailment of zinc use, results show that an iridium oxide electrode is preferable to a platinum electrode as an anode for zinc-nickel-SiO2 electrodeposition.