Microstructure and corrosion behavior of electrodeposited Zn-TiN composite coatings

In this paper, the pure Zn coating and Zn-TiN composite coatings containing four different concentrations of TiN particles were prepared on the carbon steel by direct current electrodeposition. The X-ray diffraction and scanning electron microscopy were used to study the crystal size, preferred orientation, and surface morphology of these coatings. The results show that the incorporation of TiN particles refines the crystal size of the Zn coating and results in the formation of a special surface morphology with papillary-shaped clusters structure that preferentially grows along the (100) crystallographic plane. Such a surface provides better hydrophobicity for the Zn-TiN composite coatings. The corrosion behavior of these coatings was evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy and the long-term immersion test. The results show that the incorporation of TiN nanoparticles leads to a significant increase in corrosion resistance of the Zn coating and there is an optimal addition of TiN nanoparticles to provide a best corrosion resistance for the composite coatings. Additionally, the microhardness of prepared coatings was also evaluated.