Inhibition of CO₂ Corrosion via Sustainable Geminal Zwitterionic Compounds: Effect of the Length of the Hydrocarbon Chain from Amines

Three geminal zwitterionic compounds are synthesized pursuing five parameters of green chemistry: atomic economy, environmental factor, mass intensity, mass reaction efficiency, and carbon efficiency; and evaluated as corrosion inhibitors for carbon steel (AISI–1018). The zwitterions are produced with variable length from amines (i.e., hydrocarbon chains), achieving mass reaction efficiencies higher than 80%, without the generation of wastes. The molecular structures are characterized using infrared spectroscopy and nuclear magnetic resonance. AISI–1018 steel coupons (blank corrosion) are used to test the corrosion inhibition of the geminal compounds at different concentrations (10, 25, 50, 75, and 100 ppm) in 1.0 M NaCl saturated with CO2 (pH = 3.5 and 70 °C). Electrochemical characterization is conducted using the open circuit potential (OCP) method, and polarization curves (±320 mV vs OCP) to determine the optimum concentrations in which the inhibitors decrease the corrosion rate of the steel. The corr...