Abstract1-(3-methyl-4H-1,4-benzothiazin-2-yl)ethanone (1,4-BT) was synthesised via a new mechanism. 1,4-BT was thereafter tested as corrosion inhibitor of mild steel in hydrochloric solution at 293 K by weight loss measurements and electrochemical techniques (potentiodynamic polarisation, polarisation resistance, impedance spectroscopy (EIS)). Inhibiting efficiency (E%) increased with concentration and reached highest values up to 98% even at low concentration with changing the mechanism of the corrosion process. Results obtained showed that the inhibitor studied was an efficient inhibitor, especially in cathodic domain. The temperature effect on the corrosion behaviour of mild steel in 1 M HCl with and without 1,4-BT at 5 10 -3 M was studied in the temperature range from 293 to 333 K. E% remains the same even at high temperature. The adsorption free energy and activation parameters for the mild steel dissolution reaction, in the presence of 1,4-BT, were determined. 1,4-BT is adsorbed on the mild steel surface according to a Langmuir isotherm adsorption model.

The present study attempted to investigate the best conditions for the use of a mixture of 2-mercaptobenzimidazole and alcohol ethoxylate (C13) as corrosion inhibitor of mild steel in 1 M HCl through the use of the surface response methodology. A matrix of Doelhert to 4 factors was used as the experimental design in this research as it permits the use of the response surface methodology in a spherical field. The response used in the exploitation of the design was the determination of the inhibitor efficiency. It was assessed through gravimetric measurements on samples in the absence and presence of the inhibitor. The results were confirmed using electrochemical impedance spectroscopy (EIS).

Essential oil of Juniperus phoenicea (Cupressaceae) is extracted from the natural plant collected in Morocco. Extracted by distillation, its inhibiting action on the corrosion of mild steel in 1 M acidic media has been investigated by weight loss and various electrochemical techniques. Obtained results reveal that this naturally occurring substance is a very good inhibitor. The inhibition efficiency was found to increase with the oil content, attaining 83% at 1500 ppm. The oil of Juniperus phoenicea acts as a mixed-type inhibitor. The adsorption isotherm and the thermodynamic data of adsorption and activation are herein determined and discussed.

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