Simulating study of atmospheric corrosion of Zn–Ni alloy coating on steels in marine zone: Structure and properties of artificially synthesized Ni(II)-doped zinc hydroxychloride rust particles

• Ni(II) strongly inhibits the crystallization and particle growth of zinc hydroxychloride particles.
• Adding Ni(II) lowers the affinity with zinc hydroxychloride particles to corrosive CO2 and SO2 gasses.
• Corrosion of Zn–Ni film on steel would form compact rust layer to suppress further corrosion of steel.

To simulate the atmospheric corrosion of Zn–Ni alloy coating on the steel in marine zone, artificial Ni(II)-doped zinc hydroxychloride (Zn5(OH)8Cl2⋅H2O:ZHC) rust particles were prepared by hydrolysis of ZnO particles in a mixture of aqueous ZnCl2 and NiCl2 solutions at 85 °C and were characterized by various means. Then, the Ni(II)/(Zn(II) + Ni(II)) atomic ratio in starting solution (XNi) was 0–0.10. XRD results indicated that crystallization of the layered structure of ZHC was strongly inhibited with an increase of XNi and no new particles were generated. The Ni(II) was incorporated into ZHC crystal by substitution with Zn(II) and the Ni/(Zn + Ni) molar ratio in the particles was almost consistent with XNi. The ZHC particles formed at XNi = 0 were hexagonal plate with a size of ca. 3.2 μm and a thickness of ca. 0.3 μm. Increasing XNi reduced the size and thickness of ZHC particles. Besides, addition of Ni(II) suppressed the adsorption of CO2 and SO2 gasses on ZHC, because of layered structure of this material to be disintegrated. The foregoing results suggest that atmospheric corrosion of Zn–Ni alloy coating in marine zone forms dense and compact zinc rust layer composed of fine Ni(II)-doped ZHC particles with a low affinity to corrosive gasses on the steels, leading to the suppression of further corrosion of steel. Also, role of Ni on the atmospheric corrosion of Zn–Ni alloy coating in marine zone can be suggested by studying the structure and properties of artificial Ni(II)-doped ZHC rust particles.

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