Porosity determination of nickel coatings on copper by anodic voltammetry

This paper presents the application of anodic voltammetry to determine the effective porosity in nickel coatings. The nickel coatings were obtained by electrodeposition from a Watts bath on copper substrate. This technique consists in a comparison of the charge density involved in the passivation process of the substrate without coating and that required to passivate the substrate covered with a nickel layer. The passivation solution was a 0.4 M sodium sulfide solution (Na2SO3) at 25 degreesC selected to maintain the coating inert in the potential region where substrate passivation occurs, thus preserving its integrity. The results indicate an exponential decay of the coating porosity, with respect to the deposit thickness, and a net porosity of 4 to 5%. The relation between porosity decay and deposition potential was investigated for nickel deposition from a Watts bath.