Effect of Aluminum Flakes on Corrosion Protection Behavior of Water-Based Hybrid Zinc-Rich Coatings for Carbon Steel Substrate in NaCl Environment

Abstract

In this study, waterborne hybrid organic-inorganic zinc rich coatings (ZRC) with different aluminum flake amounts were tested at low thickness in 3 wt% NaCl aqueous solution. Open circuit potential and impedance response evolution over time were measured experimentally to evaluate their anticorrosion properties. Microstructure of the investigated coatings and composition of the corrosion products were also determined by electron microscopy, X-ray diffraction and infrared spectroscopy, while the stability of the coatings was investigated via inductively coupled plasma optical emission spectroscopy. The results showed that the absence of aluminum flakes leads to a less stable matrix, unable to retain sufficient corrosion inhibitors, resulting in a shorter protection time. For an intermediate concentration of aluminum particles, good corrosion properties were observed. Corrosion products play an important role in the protection mechanism, with simonkolleite and hydrozincite accumulating over time, forming a protective layer on the substrate for several weeks. High amounts of aluminum also lead to the formation of corrosion products, but without providing a barrier effect, while rapidly consuming zinc, leading to rapid formula failure. These results indicate that the use of a controlled amount of aluminum flakes can significantly improve the corrosion protection capability of this type of coating.