Chemical inhibitors are widely used to protect metallic alloys from corrosion in aqueous environments. This Letter investigates the possible synergistic behavior of a quaternary ammonium carboxylate compound toward the development of a new system taking advantage of the surface activity of a known antimicrobial surfactant molecule, hexadecyl trimethylammonium cation, combined with a known organic corrosion inhibitor, the trans-4-hydroxy-cinnamate anion. Short-term potentiodynamic polarization (PP) studies combined with immersion in aqueous chloride solutions demonstrated the high inhibition efficiency of the combination of ions, and NMR pfg-diffusion measurements revealed micellar formation that was concentration- and pH-dependent. The NMR data suggest that speciation changes occur in the solution that correlate with enhanced corrosion inhibition efficiency at higher pH and at concentrations above the CMC of the compound. This new contribution may provide a rational molecular design toward delivering corrosion inhibitors to a metal surface through controlled speciation in solution.

A novel Brønsted acidic ionic liquid 2-ethyl imidazolium hydrogen sulfate, [2-Eim] HSO4, was synthesized. Its structure was investigated using FT-IR, 1 H NMR, 13 C NMR, UV, TGA and DTA spectra. This ionic liquid is utilized as a highly efficient and homogeneous catalyst for the promotion of hexahydroquinolines via one-pot multi-component condensation of aromatic aldehydes, dimedone, ethyl acetoacetate, and ammonium acetate at room temperature and neat conditions. Also, optimization of the reaction conditions was investigated using the response surface method {Central Composite Design (CCD)}. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst could be reused and recovered at least four times without appreciable loss of activity.

Chemical biocides remain the most effective mitigation strategy against microbiologically influenced corrosion (MIC), one of the costliest and most pervasive forms of corrosion in industry. However, toxicity and environmental concerns associated with these compounds are encouraging the development of more environmentally friendly MIC inhibitors. In this study, we evaluated the antimicrobial effect of a novel, multi-functional organic corrosion inhibitor (OCI) compound, cetrimonium trans-4-hydroxy-cinnamate (CTA-4OHcinn). Attachment of three bacterial strains, Shewanella chilikensis, Pseudomonas balearica and Klebsiella pneumoniae was evaluated on wet-ground (120 grit finish) and pre-oxidised carbon steel surfaces (AISI 1030), in the presence and absence of the new OCI compound. Our study revealed that all strains preferentially attached to pre-oxidised surfaces as indicated by confocal laser scanning microscopy, scanning electron microscopy and standard colony forming unit (CFU) quantification assays. The inhibitor compound at 10 mM demonstrated 100% reduction in S. chilikensis attachment independent of initial surface condition, while the other two strains were reduced by at least 99.7% of the original viable cell number. Our results demonstrate that CTA-4OHcinn is biocidal active and has promise as a multifunctional, environmentally sound MIC inhibitor for industrial applications.

Ionic liquids (ILs) have advantageous physical properties, which resulted in a rapid growth of research in this area in the past 15 years. One of the biggest challenges preventing the widespread use of ILs is the cost of production due to complex synthetic routes and/or expensive starting materials. Keeping in mind these industrial needs for scale-up and the desirable properties for applications in the lubrification area, here, we report the design and synthesis of four novel series of hydrophobic room-temperature ILs (RTILs) achieved from cheap and commercially available starting materials, namely, silicon-based, imidazolium-based, phosphonium-based, and monomer imidazolium-based. These syntheses were developed as expedited chemistry protocols and possess a greener synthetic profile compared to previously reported ILs of similar structures. All the RTILs were characterized by 1D NMR (1H NMR, 13C NMR, 31P NMR, 19F NMR, and 11B NMR) and 2D NMR (COSY, HSQC, and HMBC) analyses, high-resolution mass spectrometry, and chemical tests (primarily the silver nitrate test). Preliminary thermal analysis tests by thermogravimetric analysis show all novel RTILs display remarkably high thermal stabilities (386–474 °C). Differential scanning calorimetry data show low glass transitions ranging from −36 to −72 °C, which suggests good free volume and ion mobility.

Carbon steel is one of the most used construction materials and makes up the bulk of steel production in the world. However, this alloy is vulnerable to corrosion, which reduces its safety and costs trillions of dollars worldwide in terms of corrosion protection and infrastructure maintenance. Corrosion inhibitors are among the cheapest and most effective methods to minimize corrosion and maximize the shelf life of this ubiquitous alloy; however, they are often harmful to the environment. Currently there are no reports in terms of engineering design methodology to develop highly effective, advanced corrosion inhibitors. The possible synergistic behavior of a surfaceactive quaternary ammonium with a tailored carboxylate compound provides a rational molecular design toward delivering corrosion inhibitors to a metal surface through controlled speciation in solution. Here we show how entrapment and delivery of the anion inhibitor through speciation and micellar formation can lead to high inhibition efficiency, as determined by potentiodynamic polarization and electrochemical impedance spectroscopy. In particular, we demonstrate how NMR spectroscopy, pfg NMR diffusion measurements, and Cryo-TEM, taken together with molecular dynamic simulations, can reveal the micellar formation and its concentration dependence, with wormlike micelles evident at higher concentrations correlating with a dramatic increase in viscosity. This new organic corrosion inhibitor, cetrimonium 4-ethoxy cinnamate, provides significantly higher corrosion inhibition efficiency compared with the 4-hydroxy cinnamate analogue and with reduced toxic impact in the zebrafish embryo compared to the surface active CTAB often used as an antimicrobial.

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