Anti-corrosion protection of carbon steel with lidocaine in hydrogen sulfide-containing environments

In the past decade, active researches of expired drugs as inhibitors of metal corrosion are being conducted in various aggressive environments. In this work, the inhibitory effect of the expired drug Lidocaine was studied against corrosion of carbon steel in NACE and M1 model stratum waters of oil and gas fields containing 400 mg/L H2S.The concentration of the drug varied within 20-80 mg/L. The protective effect (Z) of Lidocaine (80 mg/L) is 81% and 86%, according to daily gravimetric tests, respectively, in NACE and M1 media. At 80 degrees C, the Z value increases to 85% and 95%, respectively. An analysis of the polarization curves in the media under study showed that Lidocaine slows down the cathode process in the NACE+H2S medium and both partial electrode reactions in M1 +H2S. According to impedance spectroscopy data, the surface coverage of the electrode by the inhibitor was calculated. The adsorption of Lido & scy;aine follows the Langmuir isotherm. A value of the free energy of adsorption indicates the physical nature of the drug adsorption.