Investigation of the anti-corrosive effect of tannic acid embedded in silica coatings on Zn substrates

Abstract: The replacement of environmentally harmful chromate coatings has been of great interest to the electrochemical industry. Compact silica coatings are a widely discussed inorganic coating alternative, to replace previously used toxic materials. Silica offers a feasible and simple method of passive corrosion protection, with the option of enhancement by incorporating different inhibitors into the matrix. Tannic acid is a non-toxic substance, that acts as cathodic corrosion inhibitor, by forming metal-tannate protective barriers. [1,2] The present study discusses the addition of different concentrations of tannic acid in nano-scale silica coatings, which were prepared by sol-gel technique and dip-coating method on Zn substrates. Long term corrosion measurements were carried out on the prepared substrates to check their durability and corrosion resistance. The thin layers were characterized by Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization Curves. It has been concluded that silica coatings containing tannic acid show promising EIS values and corrosion current densities, compared to the simple silica coatings. References: [1] E.Kushimerek, E. Chrzescijanska, Mater. Corros., 2015, 66(2), 169-174. [2] B. Qian, B. Han, M. Zheng, Corros. Sci., 2013, 72, 1-9.