EIS Evaluation of Cefalotine as Corrosion Inhibitor for API 5L X52 Steel Immersed in Acid Medium. Effect of [Cefalotine], Hydrodynamic Conditions, Temperature and Immersion Times

The corrosion behavior of pipeline steel grade API 5L X52 immersed in 1M HCl aqueous solution in the presence and absence of cefalotine, was evaluated using EIS and a rotating disk electrode. The effect of different experimental conditions namely: Cefalotine concentration, electrode rotation speed, temperature and immersion times on the corrosion inhibition efficiency (IE) of Cefalotine, were evaluated. It is shown that at stagnant conditions (0 rpm), the IE increased with inhibitor concentration, Fig. 1, reaching a value of ca. 87% at 25 ppm and 89% at 200 ppm. When the steel working electrode rotation speed was varied, it was found that for [Cefalotine] ≥ 25 ppm, the IE reached a maximum value, ca. 85%, at 40 rpm, however, it diminished to ca. 75% when the electrode rotation speed reached 1000 rpm. Furthermore, when the temperature of the corrosive media was increased from 25 to 45 °C, at stagnant conditions with 200 ppm cefalotine, the IE values remain to ca. ~80%. For stagnant conditions, 50 ppm cefalotine and 25 °C, an IE greater that 94% was found for the inhibitor even after 336 exposure hours to the corrosive media.