Effects of Al content on microstructure and corrosion behavior of Zn-Al alloy coatings

Alloying Zn with other metals is an alternative method to create advanced alloys with better corrosion properties, in this work the electrodeposition of Zn-Al binary alloy in sulphate -based acidic bath and with different Al2O12S3 content from 0.03 to 0.1M on a treated copper substrates was studied, the structure and microstructure of the coatings were analysed by X-ray diffraction (XRD) and scanning electron microscope (SEM) supported by (EDX) analysis, the microhardness was measured, the corrosion resistance was evaluated by potentiodynamic polarization (Tafel), the effect of Al ions was visible on the structure, (XRD) spectra showed zinc phase (eta-phase), and Al phase (alpha-Al phase) with Al peak intensity increasing along with the increase of Al concentration, the microhardness also enhanced gradually to 252.33 HV, the corrosion current density decreased by almost 13 times and the corrosion resistance was drastically improved at 0.1M Al.