Experimental and theoretical studies on the corrosion inhibition of mild steel by some sulphonamides in aqueous HCl

Abstract

Corrosion inhibition studies of mild steel in aqueous HCl by some sulphonamides namely sulphamethazine (SMT), sulphachloropyridazine (SCP), sulphabenzamide (SBZ) and sulphaquinoxaline (SQX) has been investigated using experimental techniques (such as weight loss, potentiodynamic polarization (PDP), Electrochemical Impedance Spectroscopy (EIS), Fourier transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM)) and theoretical methods (using the Density Functional Theory (DFT)). All the compounds effectively inhibited the corrosion process by becoming adsorbed on the metal surface following the Langmuir adsorption isotherm model. The electrochemical results showed that these inhibitors are mixed-type. The theoretical studies were undertaken to provide mechanistic insight into the roles of the different substituents on the corrosion inhibition and adsorption behaviour of the studied compounds. The calculated quantum chemical parameters include the highest occupied molecular orbital (HOMO), the energy of the HOMO, dipole moment and partial atomic charges, etc.The calculated molecular properties were compared across the structures of the four compounds in order to identify trends related to their reactivity and their corrosion inhibition ability. The results also show that the ability of the sulphonamides to inhibit metal corrosion is strongly dependent on the electron donating ability of the substituent group and that the preferred site for interaction with the metal surface, in all the sulphonamides, is the SO 2 group. Fig. 1 Optimised structure, highest occupied molecular orbital (HOMO) and the site for electrophilic attack (as shown by the Fukui f À function) for the studied compounds.

Experimental, quantum chemical and Monte Carlo simulation studies on the corrosion inhibition of some alkyl imidazolium ionic liquids containing tetrafluoroborate anion on mild steel in acidic medium

“…The mild steel specimens in 1 M HCl in the presence of 500 ppm of the three ILs show a less damaged surface with minor scratches that might be due to the abrasion with the SiC emery sheets. This confirms that the ILs form protective films on the steel surface and prevent direct acid attack on the mild steel [53,54].…”

Enhanced Corrosion Protection Performance by Organic-Inorganic Materials Containing Thiocarbonyl Compounds

“…The data in Table 2 indicates that the addition of thiourea increased the R1 and R2 values, and the effect is improved in the presence of thiourea. Thus, results indicate that thiourea adsorption layers are formed on the inorganic surface, representing their physical adsorption on the surface of the AZ31 Mg alloy and a more effective sealing of the porous surface against mass and charge transfer 37–41 . As shown in Table 4, the resistance values of the outer part (organic layer) increased in the presence of thiourea on the inorganic surface.…”

“…Moreover, the CPE decreased with an increase in the thickness of the organic-inorganic coating, which could be attributed to the improvement in the surface of the electrical double layer 37 . The organic-inorganic materials between the charged AZ31 Mg surface and the NaCl solution could be considered as an electrical capacitor 41,42 . This is very important because higher resistance (Rct) indicate better inhibition performance.…”

Computational study of inhibitory effect of urea, n‐allylthiourea, thiosemicarbazide, and phenylhydrazine on the aluminum surfaces

“…Such materials, which are adsorbed on the surface of the metal physically and chemically, are called corrosion inhibitors, such as organic molecules, ionic liquids, amino acid derivatives, and so forth. Although these kinds of compounds cannot always protect corroding surfaces, they reduce the rate of metal dissolution; As a result, it increases the time to use the metal or alloys …”