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

No abstract

No abstract

A detailed structural analysis suggests for intermediate TEOS to GPTMS ratios a structure of highly condensed silica-siloxane domains covalently bonded to the embedding epoxy phase. The homogeneous distribution of the quasi-spherical sub-nonmetric silica-siloxane nodes is in agreement with low surface roughness (<5 nm), observed by atomic force microscopy. This dense nanostructure results in high thermal stability (>300 °C), strong adhesion to steel substrate and excellent barrier property in saline solution, with corrosion resistance in the GΩ cm range.

No abstract

In the absence of preventive maintenance, corrosion of structural steel by the deterioration of the passive layer due to exposure to aggressive environments is the main failure factor of reinforced concrete. To overcome economic, safety, and environmental implications, present research efforts focus on eco-friendly organic–inorganic hybrid coatings to achieve effective protection of reinforcing steel. Nanostructured PMMA (poly­(methyl methacrylate))–silica coatings developed by combining reactions of the polymerization of methyl methacrylate and 3-[(methacryloxy)­propyl]­trimethoxysilane with the sol–gel hydrolytic condensation of tetraethyl orthosilicate using isopropanol as a solvent represent a promising approach to accomplish this goal. The nanoscale dispersion of silica nodes covalently conjugated with PMMA chains led to transparent, homogeneous, and pore-free coatings deposited with a thickness of 15 μm on 2D and 3D reinforcing steel. Mechanical, thermal, and surface analyses showed a strong adhesion of the coating to the substrate surface (15.9 MPa), a thermal stability of up to 256 °C, and a contact angle of about 75°. Electrochemical assays in standard 3.5 wt % NaCl solution, simulated carbonated, and alkaline concrete pore solutions confirmed effective corrosion protection, with an impedance modulus of up to 100 GΩ cm2 (at 4 mHz) and a lifetime of more than 670 days. Hence, PMMA–silica hybrid coatings are an eco-friendly and efficient alternative to protect reinforcing steel against corrosion, helping to prevent structural failures and fatal accidents.

Organic-inorganic coatings based on polymethyl methacrylate (PMMA)–silica–lithium are an efficient alternative to protect metals against corrosion. Although the preparation methodology is established and the thin coatings (~10 µm) are highly protective, the use of an environmentally friendly solvent has not yet been addressed. In this work, PMMA–silica coatings were synthesized using 2-propanol as a solvent and deposited on aluminum alloy AA7075, widely used in the aeronautical industry. Different concentrations of lithium carbonate (0–4000 ppm) were incorporated into the hybrid matrix to study the structural and inhibitive effects of Li+ in terms of barrier efficiency of the coatings in contact with saline solution (3.5% NaCl). Structural and morphological characterization by low-angle X-ray scattering, X-ray photoelectron spectroscopy, atomic force microscopy, thermogravimetric analysis, thickness, and adhesion measurements, showed for intermediate lithium content (500–2000 ppm) the formation of a highly polymerized PMMA phase covalently cross-linked by silica nodes, which provide strong adhesion to the aluminum substrate (15 MPa). Electrochemical impedance spectroscopy (EIS) results revealed an excellent barrier property in the GΩ cm2 range and durability of more than two years in a 3.5% NaCl solution. This performance can be attributed to the formation of a highly reticulated phase in the presence of Li, which hinders the permeation of water and ions. Additionally, the self-healing ability of scratched samples was evidenced by EIS assays showing a fast Li-induced formation of insoluble products in damaged areas; thus, constituting an excellent eco-friendly solution for corrosion protection of aerospace components.

No abstract