Experimental and theoretical structural analysis of Zn(II)-1-hydroxyethane-1,1-diphosphonic acid corrosion inhibitor films in chloride ions solution

This work aims to analyze, through weight loss and X-ray photoelectron spectroscopy (XPS) methods, the inhibitive films of 1-hydroxyethane-1,1-diphosphonic acid (1-hydroxyethylidene-1,1-diphosphonic acid, HEDP) and zinc(II) ions formed on AISI 1020 carbon steel when immersed in solutions containing 30 ppm of chloride ions, 50 ppm of HEDP, and three different concentrations of zinc(II) ions (14, 20, and 30 ppm). Moreover, the results of the experimental surface analyses were compared to molecular modeling Studies of the proposed HEDP-Fe(III)/Zn(OH)(2)/HEDP-Zn(II) protective film. The film presented dissimilar structures responsible for the different levels of metallic protection for each particular zinc(II) concentration. In general, the increase in Zn(II) concentration leads to more compact and adherent film formation, with decreased corrosion rates of carbon steel.