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PurposeThe purpose of this paper is to describe the behavior of salicylidene‐N‐N′‐dimorpholine as a corrosion inhibitor for zinc in hydrochloric acid and the mechanism of its action.Design/methodology/approachThe effects of various parameters on the behavior of this inhibitor have been studied using weight loss, galvanostatic polarization, and cathodic protection methods. Thermodynamic parameters and adsorption data also were utilized.FindingsThe inhibitor showed excellent corrosion inhibition (>99 percent) at effective concentration. It appeared from thermodynamic parameters that an efficient inhibitor is characterized by a relatively greater decrease (i.e. more negative) in free energy of adsorption (ΔGA°), positive values of entropy of adsorption (ΔSA°), and lower heat of adsorption (QA). Galvanostatic polarization data indicate that this is a “mixed” type inhibitor with predominant effect on the cathode. The inhibitor followed Langmuir adsorption isotherm behavior. The cathodic protection indicated that the conjoint action of the inhibitor and the cathodic current was either synergistic or additive.Originality/valueVery few inhibitors exhibit such excellent inhibitive effect on zinc in aggressive corrosive media as is shown in this paper.

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The inhibition performance of two Schiff bases, namely (A) Benzenamine, 2-chloro-N-[(4-methoxyphenyl)methylene] and (B) Benzenamine, 3-chloro-N-[(4-methoxyphenyl)methy-lene] as corrosion inhibitors for Al-Pure in 1.0 M HCl has been investigated by galvanostatic polarization measurement, electrochemical impedance spectroscopy (EIS) and weight loss method. Galvanostatic polarization study showed that two inhibitors are mixed type with predominant action on the cathode. The adsorption of inhibitors on Al-Pure surface was found to follow Langmuir adsorption isotherm and the thermodynamic parameters (E a , ∆G ads and Q ads ) were determined. Two Schiff bases have shown remarkable inhibition on the corrosion of Al-Pure in 1.0 M HCl solution. The high inhibition efficiency was attributed to the blocking of active sites by adsorption of inhibitor molecules on the metal surface.

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