Expired metformin drug as green corrosion inhibitor for simulated oil/gas well acidizing environment

Abstract In this study, expired metformin drug was evaluated for its corrosion inhibition performance in a simulated acidizing environment (15% HCl) using weight loss (at ambient and high temperatures) and electrochemical measurement techniques. The metformin drug exhibited excellent performance and the performance increases with increasing temperature and addition of KI. An inhibition efficiency of over 92% was observed at 60 °C. The potentiodynamic (PDP) measurement revealed metformin to acts predominantly as a cathodic-type inhibitor, inhibiting mainly the cathodic hydrogen evolution half-reaction. The SEM/EDS, AFM surface morphology and FT-IR analyses of the corrosion product after 24 hours immersion in the blank and metformin inhibited solutions provide evidence of adsorption of metformin molecules on the steel surface, thus forming a protective film that blocked the steel surface from the aggressive acid attack.