Investigation of the inhibition performance of a newly synthesized Schiff base and a mono-cationic surfactant for the protection of carbon steel tubulars during oil and gas well acidization.

This study evaluates the corrosion inhibition effectiveness of a newly synthesized Schiff base and its corresponding cationic surfactant on carbon steel exposed to an acidic environment consisting of 1.0 M HCl. The evaluation was conducted using gravimetric mass-loss tests, potentiodynamic polarization techniques, electrochemical impedance spectroscopy, scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), and density functional theory (DFT) calculations. Experimental results showed that both tested inhibitors were highly effective in reducing the corrosion rate; protective efficiency increased with inhibitor concentration and decreased as the temperature rose. The cationic surfactant demonstrated superior performance, achieving a maximum protective efficiency of 92.28% at a concentration of 5 × 10-3 mol L-1 and a temperature of 25 °C, whereas the Schiff base recorded a value of 71.65%. Electrochemical analyses demonstrated that both inhibitors suppress anodic and cathodic reactions through adsorption onto the carbon steel substrate, following the Langmuir adsorption model. Thermodynamic and quantum chemical analyses confirmed that the inhibition mechanism is primarily based on physisorption, with a chemisorption component. SEM and EDX analyses confirmed the formation of a protective adsorbed layer on the metal surface. Overall, the synthesized cationic surfactant exhibited promising corrosion inhibition performance under the investigated laboratory conditions, indicating its potential relevance to acidic environments encountered in petroleum-related operations. Further evaluation under more representative acidizing conditions is required to establish its practical field applicability.