Synthesis of substituted triazines and evaluation of their corrosion inhibition performance on Fe(100) in 1 M HCl: A combined experimental and DFT study

This study aimed to evaluate the effectiveness of synthesized substituted triazine, namely 4,6-dichloro-2-morpholine-1,3,5-triazine (DMT), 4,6-dichloro-2-anilino-1,3,5-triazine (DPT), and 4,6-dichloro-N-methylanilino-1,3,5-triazine (DNT), in inhibiting corrosion on mild steel (MS) into 1 M HCl solution. The methods used included electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), weight loss analysis, and density functional theory (DFT) calculations. Thermogravimetric analysis (TGA) was performed on the DMT, DPT, and DNT inhibitors to determine the degradation temperature. It was observed that the mass loss of DMT, DPT, and DNT begins when the temperature reaches 85.91˚C, 181.07˚C, and 253.82˚C, respectively. The results of the EIS approach suggested that an increase in inhibitor concentration for each inhibitor causes an increase in polarisation resistance, which increase the inhibition efficiency. The PDP results shows that the adsorbed inhibitor molecules affected both the cathodic and anodic reactions. According to the weight loss analysis the inhibition efficiency (%IE) increases with the concentration of the inhibitor and decreases with increase in temperature. The highest inhibition efficiency of DMT, DPT, and DNT was observed at a concentration of 0.005 M with 93.87%, 90.20%, and 87.95 respectively, at 303 K. The adsorption of all inhibitors followed the Langmuir adsorption isotherm. The SEM/EDX confirms that DMT, DPT, and DNT inhibitors formed a protective film on MS surfaces, protecting them from a corrosive environment. The DFT/PBE/GGA/DNP-3.5 computational analysis revealed binding energy values that confirm all inhibitor molecules are chemically adsorbed onto the Fe(100) surface. • Effectiveness of synthesized substituted triazine as corrosion inhibitors for mild steel in acidic medium • Thermogravimetric analysis (TGA) was performed on the DMT, DPT, and DNT inhibitors to determine the degradation temperature • The results of the electrochemical impedance spectroscopy approach suggested that an increase in inhibitor concentration for each inhibitor causes an increase in polarisation resistance, which increase the inhibition efficiency. • The potentiodynamic polarization results show that the adsorbed inhibitor molecules affected both the cathodic and anodic reactions.