Quantum chemical study of organic inhibitors of corrosion and hydrogen absorption An investigation of the mechanism of bainite transformation in experimental 0.2c-1v-2mn steel An investigation of the mechanism of bainite transformation in experimental 0.2c-1v-2mn steel

Abstract

Results of quantum chemical calculations of the molecules of organic inhibitors (Oin) of corrosion and hydrogen absorption by metals (particularly, p-R-C 6 H 4-SO 2-NH 2 where R= F, Cl, Br, CH 3) both in free state and adsorbed on cluster modeling aluminium surface containing 20 atoms of Al are compared to experimental data on efficiencies of protective action (EPA) against corrosion by this metal. Energies of boundary orbitals (HOMO, LUMO) and dipole moments of isolated molecules of Oin as well as changes of atomic charges on Oin atoms when Oin molecule adsorbed have been computed using semi-empiric MNDO quantum chemistry method. It was found that correlation coefficients between EPA and changes of electric charge on N atom [∆Q(N)] and O atom [∆Q(O)] due to adsorption of Oin on the metal surface are the most significant. At adsorption and eventually the protection action of Oin, the specific role of polar groups (such as hydroxile) and specific role of heteroatoms (such as N, S etc) in the framework of the concepts of molecular orbitals and donor-acceptor interaction between adsorbent and adsorbate.

Modelling Macroscopic Properties of Organic Species on the Basis of Quantum Chemical Analysis (on an Example of Inhibiting Efficiency of Ureides and Acetylides against Corrosion)

“…In Table 7, EDTA designate ethylendiaminetetraacetic acid derivatives, NTA -nithrilotriacetic acid derivatives, and MATA -derivatives of methylaminetetraacetic acid. [5][6][7][8]10], the results brought above in Tables 7 and 8 mean that the inhibitive properties of the selected ureides under chosen conditions are based on electron donating rather than accepting properties of their molecules.…”

“…Quantum chemical descriptors were obtained by means of GAUSSIAN-94 application in DFT/3-21G* basic set after preliminary optimization of molecular geometrical parameters in 3-21G basis, and also by means of MNDO and PM/3 semi-empirical methods. The selected QCD were: Mulliken charges on heteroatoms; energies of the boundary molecular orbitals and the power gap value; electrical dipole moment of IN molecule; so called hardness and softness of molecules as introduced in other articles and monographs [7][8][9]. The isolated molecules were studied by means of quantum chemical methods when arranged in series on the basis of generality of their structures; for such series, the correlation factors have been calculated.…”

“…By means of different quantum chemical methods (PM/3, MP/3, MNDO, ab initio), various properties of individual chemical species (including organic) have been rather successfully explained so far: efficiencies as anti-corrosion inhibitors [1][2][3][4][5][6][7][8][9][10] (also as inhibitors of hydrogen absorption by metals) [5][6][7][8][9][10], efficiencies of species as biocides e.g. against sulfate reducing bacteria (SRB) [7][8][9][10]; wide range (scope) of medical (pharmaceutical) [21] or, generally, biological activity [11] or properties in relation to important chemical applications (EFG in NQR) [12] of various individual substances can also be well explained by means of analysis of certain quantum chemical characteristics -descriptors QCD [13] available for the respective molecules, provided the chemical structure of corresponding species is known. Best if the species in a series, being in fact different from one another, also have similarities like common structural part.…”

Experimental and Quantum Chemical Study of Quinone Derivatives as Inhibitors of Corrosion and Hydrogen Absorption by Steel

“…2). Already very small concentrations of OC (1 and 2 mMol⋅dm -3 ) in the media lead to fast decrease of bacterial titer and production of biogenic Н 2 S. It is known [8,9] that pH= 7.0…7.8 is optimal for the development of D. desulfuricans, however wider рН range is bearable (5…9.5). In a media inoculated by bacteria in the absence of OC by the 4 th day of exposure maximum of their development is observed at pH=6.0…9.0 therefore in this pH range corrosion at the presence of SRB is maximal.…”

“…Their preparation included polishing by micron electrocorund paper, degreased with ethanol, UV sterilized and exposed for 168 h in water-salt media inoculated by Desulfovibrio desulfuricans SRB (the accumulating culture has been prepared preliminarily based on natural MO by multiple successive re-inoculation of probes from Parkovy stream (Kaliningrad) on elective growth medium Postgate B). Earlier [7][8][9] it was shown that 168 h is sufficient to complete the life cycle of D. desulfuricans in a limited volume of hermetically sealed vessel. During the samples exposure, pH, redox potential E h , concentration of biogenic Н 2 S in the media (by means of sedimentation iodometric titration), count of germs (in phase contrast using LOMO Biolam microscope in Goryayev camera), and electrode potential of steel φ.…”