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Abstract Organic-inorganic hybrid sol-gel coatings are an effective method to improve the corrosion resistance of magnesium and its alloys. Accordingly, in this work, tetraethylorthosilicate and methylthreeethoxy silane with good mechanical and chemical barrier properties were used to prepare the sol-gel coatings. Alanine, glutamine, and methionine were added as green inhibitors to the coatings. It was found that among the inhibitors studied, the most enhanced performance is related to 0.5 wt% of methionine with the total corrosion resistance of 47 kΩ cm2. The effect of cloisite Na+, cloisite 20A, and cloisite 30B as nanoparticle additives was also investigated. The results indicated that cloisite Na+ with the composition of 0.5 wt% shows more enhanced performance than the others. Simultaneous presence of the optimum contents of methionine and cloisite Na+ in the coatings demonstrated their synergistic effect, where R total became 434 kΩ cm2. Barrier properties of the prepared coatings were examined by electrochemical impedance spectroscopy and their characterization was performed by scanning electron microscopy, atomic force microscopy, Fourier transform infrared, and X-ray diffraction techniques. Highlights • Effect of MMT nanoparticle and amino acid on corrosion resistance of a sol-gel coating. • Barrier properties of the coating were examined by EIS. • Coating characterization was performed by SEM, AFM, FT-IR, and X-ray diffraction. • Of nanoparticles and amino acids, cloisite Na+ and methionine show better performance. • Simultaneous presence of cloisite Na+ and methionine increases the resistance remarkably. [ABSTRACT FROM AUTHOR]

The weak corrosion resistance of mild steel (MS) is considered a severe problem in many industrial applications. The application of corrosion inhibitors is suggested to mitigate the corrosion of steel. Within this framework, a series of novel inhibitors, including 4-ferrocenylbutyl formate, 4-ferrocenylbutyl acrylate, and 4-ferrocenylbutyl phenylacetate, was synthesized and subsequently characterized using 1H NMR, 13C NMR, and FT-IR spectroscopies. The corrosion inhibition properties of synthesized components were evaluated for MS in 1 M HCl solution through electrochemical impedance spectroscopy (EIS), Tafel, Atomic force microscopy (AFM), and scanning electron microscopy (SEM). SEM images showed the presence of a protective layer on the steel surface in the presence of inhibitors. This thick layer, visible to the naked eye, is responsible for a significant resistance against corrosion. EIS data indicated that the inhibition efficiency of 4-ferrocenylbutyl formate (C) increased from 92% to 94% after 14 days of immersion in 1 M HCl. Furthermore, the results show that the R ct of inhibited MS after 2 h increased from 57 to 880 Ω cm2 in 4 mM C inhibitor, and it enhanced to 1870 Ω cm2 after 170 h toward the uninhibited surface. Proposed inhibitors have extraordinary adsorption abilities on the metal surface to increase corrosion protection, improving this adsorption over time. Besides, the potentiodynamic polarization results disclosed that steel corrosion protection after two weeks of immersion in the acidic solution containing (C) inhibitor was about 20 times higher than the inhibitor-free solution. Synthesized ferrocenylbutyl derivatives can be utilized for prolonged corrosion inhibition purposes. Furthermore, density functional theory calculations revealed a linear correlation between the adsorption energies and charge-transfer values of studied 4-ferrocenylbutyl derivated and their inhibition capacity. [Display omitted] • Three components based on 4-ferrocenylbutyl Were synthesized. • The synthesized compounds were used as inhibitors for mild steel. • The inhibitors exhibited 96.78% inhibition efficiency after 14 days immersion in 1 M HCl. • DFT calculations disclosed that there were very strong interactions between inhibitors and the metal surface. [ABSTRACT FROM AUTHOR]