Application of Polarization Measurements for the Calculation of the Current Efficiency

Abstract

A method for determining the Faraday current efficiency (Ce_F) based on the ratio of partial winning currents of metal and hydrogen is considered. To calculate the magnitude of Ce_F based on polarization measurements, it is necessary to know the working current density and potential (E_i), at which metal deposits in the corresponding solution, as well as the kinetic parameters of hydrogen evolution for determining the partial current density of hydrogen (\({{i}_{{{{{\text{H}}}_{{\text{2}}}}}}}\)) at this potential. Using the proposed method, the current efficiency for nickel extraction and deposition of the nickel coating from solutions containing nickel sulfate at a current density of 300 A/m² is calculated. The kinetic parameters of hydrogen evolution are determined from the polarization curve found for the supporting electrolyte solution containing magnesium sulfate in an amount of 120 g/L and boric acid in an amount of 18 g/L at pH 3.9. The equation for the calculation of the partial current density of hydrogen evolution for any potential by kinetic parameters is derived. The use of kinetic regularities allows us to calculate Ce_F of nickel in sulfate solutions of different compositions with pH 3.0 and 4.1. The calculated values of Ce_F coincide with the current efficiency determined by the gravimetric method using a copper coulometer in the limits of the statistical error. It is shown that the division of the commercial characteristic of the “total current efficiency” (Ce_Σ) into Faraday (Ce_F) and apparatus (Ce_ap) characteristics in combination with the method of partial polarization curves makes it possible to find additional information on the degree of perfection of the production process.