Effects of silica nanoparticle Co-deposition on macrothrowing power of zinc-nickel alloy plating from an acid sulfate bath

Abstract

Zinc -nickel-SiO 2 electrodeposits have been produced from an acid sulfate bath. The co-deposition behavior of SiO 2 and the macro throwing power of plating baths were examined. The presence of SiO 2 nanoparticles in the plating bath appears to change the alloy deposition behavior. The rate of nickel deposition was considerably decreased by the presence of SiO 2 nanoparticles in the bath. The macro throwing power of plating was improved by adding SiO 2 nanoparticles to the bath. At an early stage of electrodeposition, it seems that the SiO 2 nanoparticles act as a nucleus for the precipitation. The SiO 2 nanoparticles did not disperse uniformly in a plating film; they distributed only in a SiO 2 rich layer (-50 nm thick) that formed beneath the surface. In addition, this SiO 2 rich layer can improve anticorrosive performance. Therefore, zincic use can be suppressed because fi lm thickness can be reduced compared to zinc and zinc -nickel alloy electroplating.