Characterization of corrosion products of Zn and Zn–Mg–Al coated steel in a marine atmosphere

• The corrosion behaviour of Zn–Mg–Al alloy in marine environment is characterized.
• Zn–Mg–Al alloy shows a better corrosion resistance than Zn.
• Strong enhancement of NaZn4Cl(OH)6SO4·6H2O in the corrosion products is observed.
• Al3+ and Mg2+ induced quenching effects in corrosion activity are described.

The corrosion behaviour of pure zinc and zinc–magnesium–aluminium alloy (ZMA) has been studied during 6 months of exposure in marine environment (Brest, France). The composition of corrosion products is analysed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). An improved corrosion resistance of ZMA is observed. This improvement is found to be connected to Mg2+ and Al3+ induced quenching of corrosion activity and to the enhancement of NaZn4Cl(OH)6SO4·6H2O in the formed corrosion product.