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In this paper, the main aim is to study the synergistic effects of alkanethiols upon inhibition of Schiff bases, N,N′‐ethylen‐bis and N,N′‐ortho‐phenylen‐bis in 0.5 M sulphuric acid solutions.

Measurements were carried out in a three‐electrode cell assembly connected to the corrosion measurement system using software for Tafel polarization. Impedance measurements were carried out at open circuit potential using an electrochemical interface and frequency response analyzer at frequencies from 100 kHz to 10 MHz.

Results obtained revealed that at high concentrations, each of the investigated Schiff bases and 1‐dodecanethiol (DT) were good inhibitors when added separately to the corrosive media. The decrease in corrosion rate was associated with an increase in their concentrations. It was found that the presence of DT together with Schiff bases in corrosive medium increased inhibition effect, especially at low concentrations. Synergistic effect is discussed from viewpoint of their co‐adsorption. The adsorption of combined inhibitors was found to follow Langmuir isotherm. Thermodynamic calculations revealed that adsorption of combined inhibitors had a physical nature.

In order to improve further the performance of Schiff bases and identifying their synergistic effects with other additives it is suggested that some more researches on other Schiff bases with other alkanethiol molecules must be done.

The results of this paper can be used for acid cleaning of carbon steel in which suitable inhibitor systems with the highest efficiency is required.

This paper reveals that the presence of DT molecules in solution encourage the adsorption of Schiff bases by facilitating the electrostatic co‐adsorption of Schiff base molecules through a synergistic effect.

Aims to investigate the inhibitive effect of the new series of Schiff base molecules, namely, N, N′‐ethylen‐bis(salicylidenimine) [S1], N, N′‐isopropylen‐bis(salicylidenimine) [S2] and N, N′‐Ortho‐phenylen acetyl acetone imine, (2‐hydroxy Benzophenone imine) [S3] on corrosion of copper during acid pickling treatment in 1 M HCl solution. Effects of concentration and temperature on the inhibition efficiencies of the selected Schiff bases have been studied systematically.

All inhibition experiments were conducted on copper sample in 1 M HCl solution. Weight loss measurements were carried out according to the ASTM standard procedure. Polarization curves and impedance spectra were carried out in a three‐electrode cell assembly connected to an EG&G potentiostat M273 and frequency response analyzer M1025.

Results obtained revealed that the studied Schiff bases act predominantly as cathodic inhibitors. The variations in inhibition efficiencies mainly depend on the type and nature of the inhibitors. Polarization and ac impedance measurements carried out at different concentrations of studied Schiff bases revealed that these compounds are adsorbed on copper surface and the adsorption obeys Langmuir adsorption isotherm. From the adsorption isotherms, the values of equilibrium constant, K_ads, and the free energies of adsorption, ΔG_ads, were calculated. The associated activation energy of corrosion and other thermodynamic parameters such as enthalpies and entropies have also been determined.

The presence of high efficiency and low cost inhibitors is essential in acid pickling treatments for protection of copper and lowering of acid consumption. In comparison with conventional copper corrosion inhibitors such as benzotriazole, this result would be considered as a step forward in determination of new corrosion inhibitor.

This paper reveals that Schiff bases can be successfully used for protection of copper surface in acid pickling solutions.

To study the effects of isomers of organic compounds such as phenylenediamine, toluidine and nitroaniline as inhibitors for the corrosion of carbon steel in sulfuric acid.

Standard methods have been adopted in this study such as weight loss, polarization tests, impedance measurements and hydrogen permeation studies to find out the corrosion behavior of carbon steel in sulfuric acid with and without inhibitors.

All the selected isomers inhibited the corrosion. The best performance was found in ortho‐phenylenediamine when compared with other inhibitors under study.

It clearly shows the effect of isomers of phenylenediamine, toluidine and nitroaniline. The method of study may be applicable to find out the performance of other isomers of organic compounds. As these isomers behave as good inhibitors in sulfuric acid, these may be tried as inhibitors in other acids. Hence, this study is useful to academics and researchers in the field of corrosion science and engineering.