Hybrid sol-gel coatings were prepared by using mixtures of γ-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethylorthosilicate (TMOS) as organopolysiloxane precursors and piperazine as a corrosion inhibitor [1]. The sol-gel films were characterized by using Fourier transform infrared spectroscopy (FTIR), liquid state Si liquid-state nuclear magnetic resonance spectroscopy (²⁹Si NMR) and viscosity measurements. The corrosion performance of the resulting coatings was analysed by using Global and Local Electrochemical Impedance Spectroscopies (EIS, LEIS). The study shows that these new coatings have promising anticorrosive properties when they are used for the corrosion protection of AA2024-T3 alloys in contact with NaCl aqueous solution.

The incorporation of piperazine additionally results in more effective barrier proprieties and improved corrosion protection of AA2024-T3 alloys acting firstly as a catalyst for Si-OH condensation during the polymerization of the organopolysiloxane network increasing film thickness and secondly as a metal corrosion inhibitor of the metal substrate in the base of pores of the sol-gel film.

Acknowledges:

This work was supported by the Ministry of Economy and Competitiveness of Spain (Project MAT2015-65445-C2-1-R) and Comunidad de Madrid (Project S2013/MIT-2862-MULTIMAT-CHALLENGE).

References

D.J. Carbonell, A. García-Casas, J. Izquierdo, R.M. Souto, J.C., Galván, A. Jiménez-Morales, Scanning electrochemical microscopy characterization of sol-gel coatings applied on AA2024 substrate for corrosion protection, Corrosion Science, 111 (2016) 625–636.