Electrochemical modification of Bi2S3 coatings in a nickel plating electrolyte

The electrochemical behavior of Bi2S3 coatings in Watts nickel plating electrolyte was investigated using the cyclic voltammetry, electrochemical quartz crystal microbalance, X-ray diffraction, and energy dispersive X-ray analysis methods. During the bismuth sulfide coating reduction in Watts background electrolyte in the potential region from -0.4 to -0.6 V, the Bi2S3 and Bi(III) oxygen compounds are reduced to metallic Bi, and the decrease in coating mass is related to the transfer of S2- ions from the electrode surface. When the bismuth sulfide coating is reduced in Watts nickel plating electrolyte, the observed increase in coating mass in the potential region -0.1 to -0.4 V is conditioned by Ni2+ ions reduction before the bulk deposition of Ni, initiated by Bi2S3. In this potential region, the reduction of Bi(III) oxygen compounds can occur. After the treatment of as-deposited bismuth sulfide coating in nickel plating electrolyte at E = -0.3 V, the sheet resistance of the layer decreases from 10(13) to 500-700 Omega cm. A metal-rich mixed sulfide Ni3Bi2S2-parkerite is obtained when as-deposited bismuth sulfide coating is treated in Watts nickel plating electrolyte at a potential close to the equilibrium potential of the Ni/Ni2+ system and then annealed at temperatures higher than 120 A degrees C.