Corrosion behavior of Zn-Al alloys in saturated Ca(OH)2 solution

- Corrosion behavior of Zn-Al alloys in saturated Ca(OH)2 solution was studied with pure zinc as a reference.
- Zn-Al alloys presented poor corrosion resistance compared with pure zinc.
- The formation of aluminum hydroxide hydrate (Ca2Al(OH)7·3H2O) on the surface of the Zn-Al alloys was more porous than calcium hydroxyzincate (Ca(Zn(OH)3))2·2H2O) by which gave the Zn-Al alloys a high corrosion rate.
- The corrosion rates of the Zn-Al alloys increased with increasing aluminum content in the alloys.

The influence of aluminium content on the corrosion behavior of Zn-x%Al alloys (x = 0, 0.2, 1, 3 and 6) exposed in aerated saturated Ca(OH)2 solution was investigated using open circuit potential, potentiodynamic polarization, SEM, EDS and XRD techniques. The passivation of the five samples was observed with the prolonging of immersion time. The corrosion rates of the five samples increased in the order of Zinc > Zn-0.2%Al > Zn-1%Al > Zn-3%Al > Zn-6%Al. The formation of calcium aluminum hydroxide hydrate(Ca2Al(OH)7·3H2O) loosened the corrosion product layer, which was responsible for the poor corrosion resistance of Zn-Al alloys compared with pure zinc.