New surfactants N‐alkyl‐N,N‐dimethyl‐N‐(3‐thienylmethylene)ammonium bromides: Preparation and anticorrosion evaluation

Abstract

A new series of N‐alkyl‐N,N‐dimethyl‐N‐(3‐thienylmethylene)ammonium bromides (designated as NTA‐n, n = 8, 10, 12, 14, and 16) were synthesized. The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization showed that NTA‐n could protect availably X70 steel from attack of HCl with an inhibition efficiency of about 95%. And the inhibition ability follows the following sequence: NTA‐8 < NTA‐10 < NTA‐12 < NTA‐14 < NTA‐16, suggesting that prolonging alkyl chain may enhance the inhibition capacity of the molecules. Theoretical investigation backs up well the experiment results. The correlation of theoretical calculation with the experiment results illustrated clearly double logarithmic relations between the corrosion current and the computed quantum chemical parameters such as the highest occupied molecular orbital energy ( E HOMO), energy gap (ΔE), molecular volume ( ν), electronegativity ( χ), the total energy of iron crystal with the adsorbed inhibitor molecule ( E total), the interaction energy of Fe (1 0 0) surface and inhibitor molecules ( E inhibitor), while an equation resembling Hammet relation was existed between the corrosion currents and the fraction of electrons transfer (ΔN). These linear correlations suggest the relation of the inhibitor structure with its inhibition activity: long alkyl chain and electron donating groups in NTA‐n will enhance the corrosion efficiency.

Electrochemical and theoretical assessment of the effect of two biocides on the corrosion of petroleum steel in sulfur‐polluted Black Sea water

“…The electronic properties of the biocides, effects of the frontier molecular orbital energies, the differences between lowest unoccupied molecular orbital (LUMO), and highest occupied molecular orbital (HOMO) energies (Δ E = E LUMO − E HOMO ) were investigated. Following Koopmans’ theorem, different intrinsic molecular quantities like electronegativity ( χ , a measure of the power of a group of atoms to attract electrons towards itself), global hardness ( η , a parameter related to the resistance of an atom to a charge transfer), and global softness ( σ , which shows the reactivity of the inhibitor molecules in terms of charge transfer), electrophilicity ( ω , a descriptor of reactivity that allows a quantitative classification of the global electrophilic nature of a molecule within a relative scale and is effectively the power of a system to soak up electrons), and so forth, which are supposed to influence the overall reaction between two interacting systems, have been calculated …”

Inhibition of Copper Corrosion in Acid Medium by Imidazole-Based Compounds: Electrochemical and Molecular Approaches

“…Moreover, the surface coverage (θ), calculated from equation 22, increases as the inhibitor concentration also increased. Thus, the Langmuir isotherm model 68 was applied according the equation 23. In equation 22, C Inh is the inhibitor concentration and K ads is the equilibrium constant for the adsorption/desorption process.…”