Formation of corrosion-resistance films on Al–Zn–Mg alloy by steam coating using acidic Zn(NO<sub>3</sub>)<sub>2</sub> aqueous solutions

Abstract

Corrosion resistant films were fabricated on Al–Zn–Mg alloy by steam coating using Zn(NO3)2 aqueous solution at different concentrations. XRD patterns and FT-IR spectra demonstrated that nitrate type Zn–Al layered double hydroxide (LDH) and ZnO films were formed on the Al–Zn–Mg alloys by steam coating at the temperatures of 373 to 433 and 473 K, respectively, using Zn(NO3)2 aqueous solution at 1000 mM. γ-AlO(OH) films were found to be prepared on the Al–Zn–Mg alloys by steam coating at 513 K using Zn(NO3)2 aqueous solutions at the concentrations of 1 to 100 mM. The corrosion resistance of the films was investigated by potentiodynamic polarization curve measurements. The polarization curve measurements revealed that the γ-AlO(OH) films prepared by steam coating at 513 K using 1 mM of Zn(NO3)2 aqueous solution was most effective to suppress pitting corrosion and anodic current density.