Corrosion behavior of Zn-Cu-Ti and Zn-Cu-Ti-Mg alloys in NaCl solution

In the present investigation the microstructure and corrosion behavior of Zn-Cu-Ti and Zn-Cu-Ti-Mg alloys in 3.5wt% NaCl solution were studied through scanning electron microscope, electron probe microanalysis, X-ray diffraction, polarization measurements and immersion tests. The Zn-Cu-Ti exhibited eutectic structure with rod-shaped TiZn15 phase, while the Zn-Cu-Ti-Mg mainly consisted of Zn matrix, TiZn15, tau(2)-Cu2TiZn22 ternary phase and Zn-Mg intermetallics along the grain boundaries. It was observed that in the corrosion products of both Zn-Cu-Ti and Zn-Cu-Ti-Mg alloys, the main phases were ZnO and Zn-5(OH)(8)Cl-2 center dot H2O. The corrosion tests showed that the cathodic process was suppressed and the weight gain decreased for Zn-Cu-Ti-Mg alloy in 3.5wt% NaCl solution. The better corrosion properties of Zn-Cu-Ti-Mg was owed to the formation of a more compact and protective corrosion layer arising from the increased intensity of Zn-5(OH)(8)Cl-2 center dot H2O.