The effect of indole on kinetics of electrodeposition and morphology of cadmium and nikel coatings

Issue 24(3) 2019
Pages 46-55

O.A. Duran Delgado, Southern Federal University, Rostov-on-Don, Russian Federation

L.M. Skibina, Southern Federal University, Rostov-on-Don, Russian Federation


Keywords: electrodeposition, nickel, cadmium, indole, kinetics, coatings, cyclic voltammetry, adsorption, surface morphology

http://www.doi.org/10.31615/j.corros.prot.2019.93.3-6

 

The kinetics of electrodeposition of cadmium and nickel in the presence of the addition of indole was studied by the methods of cyclic voltammetry and galvanostatic measurements. The results of cyclic voltammetry show that the deposition of metals in the studied systems is controlled by the diffusion stage. Analysis of cyclic voltammograms taken at different potential scan rates indicates that the process is irreversible in the case of nickel. With the addition of indole, the redox potentials of cadmium and nickel are shifted to the negative region, indicating that the cathodic reaction is inhibited. A comparison of the transfer coefficients α shows that with an increase in the indole concentration, the irreversibility of the cathode process increases, and the maximum inhibition is observed at an additive concentration of 5∙10-3 mol/l. The study of the adsorption of the additive, carried out by the impedance method, indicates an increase in the surface concentration of indole with an increase in its volume concentration. The analysis of capacitive curves shows that the indole is more efficiently adsorbed on the surface of the catalytically active nickel, which leads to an increase in the irreversibility of the cathode process in its presence. The method of scanning electron microscopy was used to assess the morphology of the precipitation obtained. An improvement in the microstructure of the coatings obtained in the presence of indole was shown, compared with samples obtained without an organic additive, which suggests a significant improvement in their technological and anti-corrosion characteristics.