Electrochemical and Quantum Chemical Investigation of Some Azine and Thiazine Dyes as Potential Corrosion Inhibitors for Mild Steel in Hydrochloric Acid Solution

Abstract

The inhibition performances of some selected azine and thiazine dyes, namely, Neutral Red (NR), Azure A Eosinate (AAE), Toluidine Blue (TB), phenosafranin (PS), and Rhodanile Blue (RB), on mild steel corrosion in hydrochloric acid solution was studied the using electrochemical impedance spectroscopy (EIS) and Tafel polarization techniques. Quantum chemical calculations based on the density functional theory (DFT) and semiempirical (PM3) methods were used to investigate the reactivities and selectivities of the studied cationic dyes. The effects of inhibitor concentration on the inhibition efficiency have been studied. Inhibition efficiency increased with increase in concentration of all the studied cationic dyes within the concentration range 100−500 ppm. Potentiodynamic studies revealed that all the inhibitors are of mixed type. The results obtained from the EIS studies showed good agreement with the results from potentiodynamic polarization techniques. The quantitative structure−activity relationship (QSAR) approach was also used to correlate the quantum chemical parameters with the experimentally determined inhibition efficiencies. The results show that thiazine dyes are better corrosion inhibitors than azine dyes; however, when azines contain more electron donor centers than thiazines, they are preferred as corrosion inhibitors to thiazine. Hydrogen bonding could be one of the possible physisorption mechanisms for the adsorption of the selected dyes onto the metal surface because of the many hydrogen bond donor centers in the studied compounds. QSAR results show good correlations between a number of quantum chemical parameters and the determined inhibition efficiency.

Dry and wet lab analysis on benzofused heterocyclic compounds as effective corrosion inhibitors for mild steel in acidic medium

“…Following results were observed by the comparison of molecular descriptors for neutral and protonated species: (i) E HOMO is lowered (by 4.47-4.37 eV) in the protonated than in the neutral species, which indicates that protonation decreases the electron donating tendency of the inhibitors. According to Ebenso et al, protonation of inhibitor molecule results in an increased nuclear charge so that the nuclear charge pulls more strongly the outer electrons [58]. Hence the ionization energy required to remove the outer electron is higher in the protonated inhibitor than in the neutral species.…”

Potential of Azadirachta indica as a green corrosion inhibitor against mild steel, aluminum, and tin: a review

“…These studies are assisting in reducing the experimental costs for testing many compounds with the objective of synthesizing the ones that have high promise for corrosion inhibition. Density functional theory (DFT) and molecular dynamics (MD) approaches are increasingly used for predicting the inhibition potential of compound for corrosion on geometrical, electronic, and binding property bases on metal surface Kabanda and Ebenso 2012;Ebenso et al 2012b). Recently, more corrosion publications contained substantial quantum chemical calculations and molecular dynamics simulations Kabanda et al 2013;Obot and Gasem 2014).…”

Investigation of Thermodynamic Parameters for Steel Corrosion in Acidic Solution in the Presence of N,N′-Bis(phloroacetophenone)-1,2 propanediamine

“…Among the corrosion control techniques, the development of new corrosion inhibitors have substantially increased in the recent years because it is believed to be one of the most effective and economic methods to protect metal corrosion in acidic media [5,6]. Most of the wellknown acid inhibitors are organic compounds containing N, O, P, S, and aromatic ring or triple bonds.…”

“…In general, organic compounds are effective inhibitors of aqueous corrosion of many metals and alloys. The use of chemical inhibitors to decrease the rate of corrosion processes of carbon steels is quite varied [5][6][7][8][9]. A variety of organic compounds containing heteroatoms such as O, N, S, and multiple bonds in their molecule are of particular interest as they give better inhibition efficiency than those containing N or S alone [10].…”