Realizing in-situ preparation of ZnAl layered double hydroxide film on titanium alloy through one-step hydrothermal reaction

Abstract

A hydrothermal process was proposed for in-situ preparation of ZnAl layered double hydroxides with nitrate (ZnAl-NO3-LDHs) on a Ti6Al4V titanium alloy. To destroy the dense and stable TiO2 film on the titanium alloy, mild NH4F instead of strong HF was used as a F− ion source in the growth solution of the hydrothermal reaction, and ammonia water instead of urea was used to adjust the pH value, both of which helped to realize in situ growth of ZnAl-LDHs films on titanium alloys. The structure and morphology of the LDHs films were characterized using X-ray diffraction and scanning electron microscopy. The corrosion resistance and stability of the LDHs films were evaluated using potentiodynamic polarization curves and immersion tests. The results show that a uniform ZnAl-NO3-LDHs film was formed in situ on the titanium alloy with the help of NH4F and NH3·H2O. The formation mechanism of ZnAl-NO3-LDHs on the TC4 titanium alloy was determined. The ZnAl-NO3-LDHs film improved the corrosion resistance of the titanium alloys and has the potential to improve anti-fouling properties by loading anti-fouling substances; however, the laminates of the LDHs fell off after long-term immersion in marine environments.