Dual Role of Lithium on the Structure and Self-Healing Ability of PMMA-Silica Coatings on AA7075 Alloy

Abstract

In this work, structural and active corrosion inhibition effects induced by lithium ion addition in organic-inorganic coatings based on polymethyl methacrylate (PMMA)-silica solgel coatings have been investigated. The addition of increasing amounts of lithium carbonate (0, 500, 1000 and 2000 ppm), yielded homogeneous hybrid coatings with increased connectivity of nanometric silica cross-link nodes, covalently linked to the PMMA matrix, and improved adhesion to the aluminum substrate (AA7075). Electrochemical impedance spectroscopy (EIS), performed in 3.5% NaCl aqueous solution, showed that the improved structural properties of

The Effect of the Methyl and Ethyl Group of the Acrylate Precursor in Hybrid Silane Coatings Used for Corrosion Protection of Aluminium Alloy 7075-T6

“…Hybrid sols have been prepared using TEOS and MAPTMS in the optimum ratio [5]. Since previous studies on these type of coatings were carried out on steel-based substrates [3][4][5][6] and less on Al-based substrate [8,15], we focused this study on aluminium alloy (AA) 7075-T6 substrate. This particular alloy was chosen because it is the least corrosion resistant among alloys used in the aviation industry.…”

Organic-Inorganic Hybrid Coatings for Active and Passive Corrosion Protection

“…The films with thickness between 4 μm and 6 μm present excellent adhesion to AA7075 substrate reaching values up to 28 MPa for coatings with higher Li loading [24]. The improved adhesion for lithium-rich coatings might be related to aluminum enrichment near the coating/substrate interface, suggesting a diffusion of Al from the alloy into the coating during the thermal treatment [24].…”

“…As possible mechanisms, Visser et al have proposed that the release of lithium ions from the epoxy matrix forms in the defective zone a Li/Al layer (hydrotalcite class) by a conversion process [46]. In recent work, lithium carbonate (Li 2 CO 3 ) was for the first time added (500-2000 ppm) into the PMMA-silica system, and the results revealed a dual beneficial effect of lithium on the structure and self-healing ability of the coatings on the AA7075 aluminum alloy [24]. The structural analysis of the coatings showed that the changes of the smallangle X-ray scattering (SAXS) profiles imply significant modifications in the nanostructure of the silica phase for higher lithium loadings (Figure 5a).…”

“…The self-healing process of the first recovery event was analyzed by fitting the EIS data using EEC containing a electrolyte resistance in series with two time constants, Figure 6. [24]. Copyright (2020) American Chemical Society).…”

“…Organic-Inorganic Hybrid Coatings for Active and Passive Corrosion Protection DOI: http://dx.doi.org /10.5772/intechopen.91464 In practice, however, some studied coating systems, especially those based on inhibitor-filled micro-and nano-containers, imply increasing costs, which are hardly accepted by the industry. Some recent studies reporting on incorporation of simple additives, such as PANI [20], TiO 2 [21], ZnO [22], lithium [23,24], ZrO 2 [9,25], cerium/ceria [26][27][28][29], poly(2-butylaniline) (P2BA) [30], polydopamine (PDA) [31], 2-mercaptobenzimidazole (MBI) [32], and tannins [33], among others, have shown promising results toward the development of chromium-free active coatings. This chapter comprises an overview of efficient passive organicinorganic coatings and their modified form for active protection of metal surfaces.…”