Corrosion protection of N80 steel by maleanilic and succinanilic organoselenium compounds in acidic oilfield formation water

Herein, we report the synthesis of two organoselenide-based maleanilic ( HB049 ) and succinanilic ( HB050 ) acids from the reaction of selenoamine 3 with maleic and succinic anhydrides in 65 % and 90 % yields, respectively. Their protection efficacy was evaluated towards N80 steel in simulated oilfield formation water using a range of experimental and theoretical methods. Potentiodynamic polarization measurements indicated a significant decrease in corrosion current density to 72.58 µA cm⁻² and an increase in protection efficiency to 95.7 % at a concentration of 5 × 10^-4 M for HB049 . These additives markedly suppressed both anodic and cathodic reactions, indicating a mixed-type inhibition mechanism. Electrochemical Impedance Spectroscopy measurements showed that the polarization resistance increases with concentration, reaching 8441.26 Ω cm² at 5 × 10^-4 M for HB049 . The adsorption of inhibitors on the surface of N80 steel was confirmed using Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy. It was found that HB049 and HB050 followed the Langmuir isotherm and were chemically adsorbed. Furthermore, Density Functional Theory results indicate that HB049 exhibits high electron-donating capacity, which accounts for its superior inhibitory efficiency. Additionally, Monte Carlo simulations corroborated the favorable alignment of both inhibitors in an approximately planar configuration on the Fe(110) surface, thereby maximizing surface coverage and corrosion protection.