Initial formation of corrosion products on pure zinc and MgZn2 examinated by XPS

• Atmospheric corrosion under humid air of zinc and zinc–magnesium pure phases were investigated.
• The corrosion products were characterized in depth using X-ray photoelectron spectroscopy.
• Migration of Mg atoms toward the surface was observed during ZnMg corrosion.
• The chemical reactions were different for Zn and MgZn2 corrosion leading to different corrosion products.

A corrosion behaviour study of pure phases of zinc and zinc–magnesium (MgZn2) exposed to humid air at 35 °C for 4 days is presented. For zinc, hydroxide formation at the surface and zinc oxide in the first innerlayers is observed. The corrosion of the MgZn2 leads to the segregation of magnesium at the surface to mainly form magnesium hydroxycarbonate: the presence of magnesium modifies the corrosion products. At larger depths, metallic zinc coexists with magnesium oxide and hydrozincite. The higher reactivity of MgZn2 alloy can be attributed to the interaction with carbonate ions.