Fabrication of Pb-Co-ZrO2 nanocomposite coatings and correlation of corrosion mechanisms with electronic work functions

Abstract

It is still an urgent task to design metal coatings for the development of corrosion resistance. Herein, Pb-Co-ZrO2 coating is fabricated on the surface of aluminum plates via one-step pulsed electrodeposition for corrosion resistance. The pulse frequency, current density and duty cycle are 800 Hz, 15 mA cm−2 and 20 %, respectively. In this work, the concentration of ZrO2 nanoparticles in the bath is the main operating variable. We further explored the deposition mechanism of the nanocomposite coating and demonstrated its application potential in corrosion resistance. As expected, the corrosion resistance and mechanical properties of the coatings increased and then decreased with the increase of the concentration of ZrO2 nanoparticles in the plating solution. When the concentration of ZrO2 nanoparticles in the plating solution was 15 g L−1, the Pb-Co-ZrO2 nanocomposite coating exhibited excellent corrosion resistance in 3.5 wt% NaCl solution, with an impedance modulus value (5182 Ω cm2) that was eight times higher than that of the pure Pb coating (669 Ω cm2), possessed the highest corrosion potential (- 0.60 V) and the lowest corrosion current density (3.6 μA cm−2), while also exhibiting excellent mechanical properties. The mechanism of the improved corrosion performance of the Pb-Co-ZrO2 composite coatings was further explained using DFT calculations. The results show that the coupling between the interface of Pb-Co solid solution and ZrO2 nanoparticles effectively improves the overall electron figure of merit of the coatings and triggers an obvious electron localisation, which increases the energy required for the interfacial electrons to escape from the coating interface.