Corrosion inhibition of mild steel by an eco-friendly effective chitosan ortho-vanillin Schiff base in hydrochloric acid

The corrosion inhibition performance during acid cleaning often uses harmful chemicals, or eco-friendly extracts involving complicated steps and multiple organic solvents. This study explores an environmental friendly alternative of single-step synthesized chitosan ortho-vanillin Schiff base (OVCS) and investigates its inhibition behavior for mild steel in 1 M HCl solution. The structure of prepared OVCS was characterized using FTIR. Thermogravimetric analysis suggested that the synthesized OVCS compound exhibited good thermal stability at the temperature below 200 °C. Weigh loss results indicated that OVCS compound acted as an effective corrosion inhibitor and the maximum inhibitory efficiency was up to 93.99 % at the concentration of 1000 mg/L. Potentiodynamic polarization tests revealed that OVCS worked as mixed-type inhibitor and the corrosion current density decreased from 258.8 μA·cm −2 (in the absence of OVCS inhibitor) to 18.90 μA· cm −2 (in the presence of 1000 mg/L OVCS inhibitor). The adsorption of OVCS compound onto mild steel follows Langmuir adsorption isotherm. The standard free energy of adsorption was found to be −27.59 kJ/mol, indicating both chemical and physical adsorption interactions and the coordinate covalent bonding was predominant. Thermodynamic parameters, Δ H a and Δ S a were also calculated to further illustrate the corrosion inhibition performance. This study supplies a facile and effective strategy for corrosion protection of mild steel during acid cleaning process in industrial applications.