A. Kuznetsova

Enhancement of active corrosion protection via combination of inhibitor-loaded nanocontainers.

The present work reports the synthesis of layered double hydroxides (LDHs) nanocontainers loaded with different corrosion inhibitors (vanadate, phosphate, and 2-mercaptobenzothiazolate) and the characterization of the resulting pigments by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The anticorrosion activity of these nanocontainers with respect to aluminum alloy AA2024 was investigated by electrochemical impedance spectroscopy (EIS). The bare metallic substrates were immersed in dispersions of nanocontainers in sodium chloride solution and tested to understand the inhibition mechanisms and efficiency. The nanocontainers were also incorporated into commercial coatings used for aeronautical applications to study the active corrosion protection properties in systems of industrial relevance. The results show that an enhancement of the active protection effect can be reached when nanocontainers loaded with different inhibitors are combined in the same protective coating system.

Polyelectrolyte-modified layered double hydroxide nanocontainers as vehicles for combined inhibitors

In this work, nanocontainers based on layered double hydroxide (LDH) loaded with two different corrosion inhibitors, namely 2-mercaptobenzothiazole (MBT) and cerium(III) nitrate, were prepared. MBT was intercalated into LDH galleries in anionic form by anion-exchange, while Ce3+ was fixed between polyelectrolyte layers on the surface of LDH-MBT nanoplatelets by the Layer-by-Layer (LbL) method. Both inhibitors were found in the modified LDHs (LDH-Mod) by X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy. The release studies performed by UV-vis spectrophotometry indicated that the main triggering conditions for release of MBT from LDHs changed when LDH nanoplatelets were covered with polyelectrolytes. Furthermore, electrochemical impedance spectroscopy and DC polarization were used to investigate the effect in combining MBT− and Ce3+ within the same nanocontainer, for the corrosion protection of 2024-T3 aluminium alloy directly in solution as well as in a hybrid sol–gel coating. The obtained results open prospects for application of these systems as additives in multifunctional smart coatings.

A computational UV–Vis spectroscopic study of the chemical speciation of 2-mercaptobenzothiazole corrosion inhibitor in aqueous solution

In order to understand the chemical speciation of 2-mercaptobenzothiazole (MBT) corrosion inhibitor as a function of pH, the experimental electronic absorption spectra was compared with those calculated at the EOM-CCSD, TD-M06-2X and TD-B3LYP levels of theory for several different species that may result from MBT reactions in aqueous solution. The computational spectroscopic analysis was supported by the energetics of tautomerization, deprotonation, non-covalent association and ion-pair formation reactions calculated at the M06-2X/6-31++G(d,p) level of theory. The thioketonic and deprotonated anionic forms of MBT were found to be the main species depending on the pH, while the formation of the ion-pair was also supported under basic conditions, especially when put in perspective of the release profiles of the inhibitor from nanocontainers published in the literature. The calculated energetic and electronic results were used to unveil the tautomeric, acid–base and ion-pair formation equilibrium, relevant to guide the application of MBT as a corrosion inhibitor, and establishing a foundation for future molecular modeling studies concerning the adsorption of MBT onto metal and metal alloys under different pHs.

Antimicrobial activity of 2-mercaptobenzothiazole released from environmentally friendly nanostructured layered double hydroxides

The objective of this work was to assess the antibacterial effect of 2‐mercaptobenzothiazole (MBT), used as model‐biocide, immobilized in a layered double hydroxide (LDH) structure, under different conditions of pH and salinity, envisaging possible applications of the system in active antifouling and anticorrosion coatings.

Effects of a novel anticorrosion engineered nanomaterial on the bivalve Ruditapes philippinarum

Metallic corrosion is an unsolved problem that has been minimized through the application of specialized coatings containing corrosion inhibitors, such as 2-mercaptobenzothiazole (MBT). Recently, engineered nanomaterials (ENM), such as layered double hydroxides (LDH), have been used to immobilize or encapsulate those compounds promoting their controlled release in a more eco-friendly way. The present study aims to assess the toxicity of a novel anticorrosion nano-based solution (LDH loaded with MBT) and its major compounds separately (MBT and LDH) to the clam Ruditapes philippinarum, during a short-term exposure (96 h). The endpoints were lethality and changes in the physiological and biochemical parameters. MBT induced mortality (LC20 = 78.14 mg L−1) and significant physiological and biochemical changes. Globally, these effects were more severe than those treated with LDH and LDH–MBT that still induced significant biochemical effects. The present study demonstrated the eco-friendly properties of the immobilization process of the corrosion inhibitor in the nanoclays. Effects were observed at higher concentrations than those expected to occur in the environment and therefore these novel nanomaterials can be a promising anticorrosion material with low environmental hazard and risk.