Inhibition of Iron Corrosion in HCl Solutions by N-[2-[(2-Aminoethyl) Amino] Ethyl]-9-Octadecenamide

N-[2-[(2-aminoethyl) amino] ethyl]-9-octadecenamide (AAOA) has been synthesized in the lab, then tested as an effective and economic acid inhibitor for A3 steel in an acid medium with electrochemical techniques (electrochemical impedance and polarization curve). The results show that AAOA acts as a good mixed-type inhibitor for A3 steel in 1 M hydrochloric acid (HCl) solution, and the inhibition efficiency reaches 94% at the concentration of 200 mg/L. The corrosion current density of A3 steel increases with the increasing temperature from 20°C to 60°C. Meanwhile, Langmuir isotherm is found to provide the description of the adsorption behavior of AAOA, and the value of adsorption free energy (ΔG⁰) is as low as low as −37.3 kJ/mol. One can assume the adsorption of inhibitor molecules on the metal surface is by chemisorption, which has been understood taking into account some other adsorption parameters (ΔH⁰, ΔS⁰) and the activation parameters (E_a, ΔH^*, ΔG^*).