Physico-Chemical nanomaterials science

Quantum-chemical calculation of interaction of green inhibitors with nanostructed metal surfaces
Kolylets V. I., Korniy S. A., Pokhmurskii V. I., Zin I. M.
Karpenko Physico-Mechanical Institute of the NAS of Ukraine. Naukova Str., 5, Lviv-79061, Ukraine. E-mail: kornii@ipm.lviv.ua

Nanosrtuctured surfaces of Al, Fe an Cu (as constructive metals) under the influence of environment undergo easy destruction in the stressed locations of the surface. We used quantum-chemical method PM7 to calculate geometry and electron structures of the possible departing cluster complexes Me(H2O)(Cl) and molecules of a row of green organic molecules – luteinic, gallic, dehydrogallic, ellagic, di-p-oxybenzoic, m-galloidgallic, tannine acids, as well as bio-molecules of mono- and dirhamnolipide and trihalosodimycolate. Mulliken electron charges were calculated and studied as one of the criteria for adsorption and inhibitor properties predictions for these perspective compounds against metal corrosion.
We showed that the studied molecules influence on metal surface by metal mulliken charge decrease in different degree. Small ones (the first six) lower the charge on Al, Cu and Fe in 10–12%, 6–9%, and 12–16% respectively. For tannine acid these values are better – 17%, 13% and 20%. Rhamnolipide offers the following decrease – 53%, 48% and 42%. The best results showed trihalosodimy-colate – 75%, 68% and 78%. It was found that these molecules is their flat structure may cover many adsorption sites on metals, so decreasing the possible centers of metal anode dissolution by partial electron transfer from oxygen atoms of the function groups of their molecules [1]. Such transfer from initially stable electron pairs becomes possible due to metal surface activation through stressed condition of the nanostructured metals.
In details all the structure of the adsorbed molecules becomes more flexible for electron transfer due to hyperconjugation of π-electrons. Initially stable electron pairs on oxygen atoms of functional groups resemble that of carbon rings with heteroatoms of nitrogen, sulphur etc. Thus for better anticorrosion properties we must propose large organic molecules with oxygen groups, located near each other as possible. A good example are the above green natural compound: rhamnolipide and trihalosodimycolate.

1. I. Zin, V. Pokhmurskii, S. Korniy et all. Corrosion inhibition of aluminium alloy by rhamnolipid biosurfactant derived from Pseudomonas sp. PS-17 // Anti-Corr. Meth. and Mater.-2018.-65.-P. 517-527.