Study on Electrochemical Depositing Al Anticorrosion Layer on Cast Iron Surface in AlCl₃-[EMIM]Cl Ion Liquid

Abstract

For clarifying the electrochemical deposition mechanism of corrosion-resistant aluminum coating on surface of cast iron , the aluminum coating was electrodeposited on cast iron surface in AlCl3-[EMIM]Cl ionic liquid, and the deposition electrode process and nucleation growth mechanism of aluminum electrochemical coating on surface of cast iron were studied by cyclic voltammetry and chronoamperometry. Subsequently, aluminum coating was prepared by constant current density electrodeposition, and the effect of the current density and deposited time on the corrosion resistance of cast iron deposited with aluminum coating was investigated by the AC impedance, polarization curve and salt spray test methods. Results showed that the precipitation overpotential of aluminum on the surface of cast iron was close to zero. The deposition was dominated by the mass transfer process, and the nucleation confirmed with three-dimensional instantaneous nucleation model. Comparing the cast iron sample, the self corrosion potential of the cast iron sample deposited aluminum coating shifted negatively, and the corrosion current also became smaller than that of cast iron. Moreover, the deposition current density was the decisive factor affecting the corrosion resistance of cast iron. With the increase of current density, the corrosion resistance of cast iron increased. The corrosion current value of the cast iron sample deposited aluminum coating under constant current density 30 mA/cm2 was lower one order than that of the cast iron substrate. The aluminum coating deposited for 20 min possessed small crystal grains and excellent corrosion resistance.

Keywords

• cast iron|aluminum coating|alcl₃-[emim]cl ionic liquid|electrode process|corrosion|current density|deposition time