Investigation of Nickel Carbonate as a Functional Accelerator in Zinc Phosphating: Corrosion Behavior and Electrochemical Insights

Abstract

The inherently slow reaction kinetics of zinc phosphating—primarily due to polarization caused by hydrogen evolution during the cathodic process—can be enhanced through various chemical, mechanical, and electrochemical strategies. This study investigates the role of nickel carbonate (NiCO₃) as an accelerator in improving the corrosion resistance and structural compactness of zinc phosphate coatings. Zinc phosphate layers were successfully deposited on low carbon steel substrates, both in the presence and absence of the accelerator. Nickel carbonate was added to the phosphating solution in concentrations of 0.6%, 1.2%, and 1.8%. Corrosion behavior was analyzed using potentiodynamic polarization tests in a 3.5% NaCl medium. Furthermore, Electrochemical Impedance Spectroscopy (EIS) was conducted to evaluate the compactness of the coatings in the same environment. The results demonstrated that incorporating nickel carbonate significantly improved the performance and density of the phosphate coatings. The inherently slow reaction kinetics of zinc phosphating—primarily due to polarization caused by hydrogen evolution during the cathodic process—can be enhanced through various chemical, mechanical, and electrochemical strategies. This study investigates the role of nickel carbonate (NiCO₃) as an accelerator in improving the corrosion resistance and structural compactness of zinc phosphate coatings. Zinc phosphate layers were successfully deposited on low carbon steel substrates, both in the presence and absence of the accelerator. Nickel carbonate was added to the phosphating solution in concentrations of 0.6%, 1.2%, and 1.8%. Corrosion behavior was analyzed using potentiodynamic polarization tests in a 3.5% NaCl medium. Furthermore, Electrochemical Impedance Spectroscopy (EIS) was conducted to evaluate the compactness of the coatings in the same environment. The results demonstrated that incorporating nickel carbonate significantly improved the performance and density of the phosphate coatings.