Inhibitive effect of salicylidene‐N‐N′‐dimorpholine towards corrosion of zinc in hydrochloric acid

Purpose The 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/approach The 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. Findings The 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/value Very few inhibitors exhibit such excellent inhibitive effect on zinc in aggressive corrosive media as is shown in this paper.