The effect of Al content in sacrificial zinc coating on the inhibition efficiency of cerium(III) and molybdate salts
T. T. Nguyen1,2, C. Arrighi1, T. T. Thai2, A. T. Trinh2, M-G. Olivier1
1Material Science Department, University of Mons, Place du Parc 20, 7000 Mons, Belgium
2Institute for Tropical Technology, VAST, A13 Building, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam.
E-mail: thithao.NGUYEN@umons.ac.be
Zinc is widely used as a sacrificial coating in construction, automotive industry, and in other applications. Since several decades, a large research has been carried out by alloying zinc to limit its consumption and to enhance the corrosion resistance of such coatings. Zn-Al coatings have been developed to increase the corrosion resistance since Al can form a thin Al2O3 layer improving the physical barrier properties.
Nevertheless, corrosion inhibitors are used in inorganic and organic films to reduce the required zinc coating thickness and to limit its consumption during the lifetime. In the literature, many studies have focused on the use of cerium salts to inhibit corrosion for zinc coatings. The authors have also showed that molybdate exhibits an effective corrosion inhibition for zinc coatings in case of scratches [1,2].
In this work, the effect of Al content in the zinc coating on the inhibitor efficiency of CeCl3 and Na2MoO4 salts was investigated in a neutral solution (0.1M NaCl). Three metallic coatings having different Al contents were used: pure electrogalvanized zinc, hot dip galvanized steel and Galfan coating. The corrosion performance was determined by electrochemical techniques such as Electrochemical Impedance Spectroscopy (EIS) and polarization curves. Surface analyses such as SEM and EDX were performed.
The results indicated that Ce(III) exhibited a high protection and stable effect for all substrates while MoO42- showed a lower protection strongly influenced by the Al content in zinc coatings.
References
[1] A. Kartsonakis et al. Corrosion Science 112 (2016): 289-307.
[2] Coelho, L. B., et al., Corrosion Science 175 (2020): 108893.
Acknowledgments
This work is carried out in the framework of the Research project (PRD2020) “Renforcement de l’expertise environnementale du centre de compétences en protection contre la corrosion et en électrochimie” between Institute of Tropical technology (ITT-VAST, Vietnam) and Materials Science Department, UMONS, Belgium