Inhibiting general and pitting corrosion of Ni in dilute sulfuric acid solutions with some tetrazole derivatives

Abstract

5-(Benzylthio)-1H-tetrazole (BST), ethyl-1H-tetrazole-5-acetate (ETA), and 5-(ethylthio)-1H-tetrazole (EST) were utilized to inhibit the pitting and general corrosion of nickel in dilute sulfuric acid solutions. The galvanostatic anodic polarization under a constant current and mass loss measurement complemented by a scanning electron microscope is utilized. The tetrazole inhibitors retard the pitting corrosion by shifting the pitting potential, Ep into the more noble direction while lowering the amount of electricity, Qinh, needed to attain Ep. The protection efficiency, η, increased with increasing the amount of tetrazole in the solution to follow the order EST < ETA < BST. The protection influence of such inhibitors is accompanied by the blocking of the investigated metal surface by their molecules through an adsorption process that follows Langmuir's model. The computed -∆G⸰ads values are 37.17, 36.82, and 36.57 kJ mol-1 for BST, ETA, and ETA, successively, at 298 K. Such values are harmonious with a mixed chemo-, physisorption mechanism. A coordinate link is supposed to originate between the tetrazole compound and the investigated nickel surface.