EIS Evaluation of Pantoprazole as Corrosion Inhibitor for Mild Steel Immersed In HCl 1 M. Effect of [Pantoprazole], Hydrodynamic Conditions, Temperature and Immersion Times

The corrosion behavior of pipeline steel grade API 5L X52 immersed in a 1M HCl aqueous solution in the presence and absence of Pantoprazole, was evaluated using EIS. The effect of different experimental conditions namely: Pantoprazole concentration, electrode rotation speed, temperature and immersion times on the corrosion inhibition efficiency (IE) of Pantoprazole, were evaluated. It is shown that at stagnant conditions (0 rpm) the IE increased with inhibitor concentration, reaching a value of ca. 93% at 25 ppm, which remains constant up to 200 ppm. When the steel working electrode rotation speed was varied, it was found that for [Pantoprazole] > 25 ppm, the IE reached a maximum value, ca. 95%, at 40 rpm, however, it diminished to ca. 85% when the electrode rotation speed reached 1000 rpm. Furthermore, when the temperature of the corrosive media was increased from 25 to 60 °C, at stagnant conditions with 25 ppm Pantoprazole, the IE values diminished to ca. 60%. For stagnant conditions, 50 ppm Pantoprazole and 25 °C, an IE greater that 93% was found for the inhibitor even after 700 exposure hours to the corrosive media. Lastly, the results showed that, in all cases, the Pantoprazole inhibition mechanism involves blockage of the steel surface throughout a Langmuir-type physisorption process.