Polyacrylamide as a corrosion inhibitor for mild steel in 2 M phosphoric acid: experimental and theoretical studies

• DOI: 10.1007/s11696-021-01725-5
• Publication Date: 2021-06-06T15:03:24Z
• Authors: Rasha J. Jadaa; Ahmed N. Abd; Anees A. Khadom
• Keywords: Polyacrylamide; Phosphoric acid; Langmuir adsorption model; Corrosion inhibitor

The corrosion inhibition behavior of mild steel in 2 M H3PO4 was investigated in the absence and the presence of Polyacrylamide (PAM) as a corrosion inhibitor. The influence of temperature and inhibitor concentration was studied using weight loss and electrochemical techniques. The results showed that PAM acted as a powerful inhibitor. The inhibition efficiency increased with PAM concentration and decreased with temperature. Maximum inhibition efficiency was 91.02% at 600 ppm of PAM and 30 °C. The adsorption of PAM on mild steel surface was found to fellow Langmuir adsorption isotherm. The value of the adsorption free energy was negative and lower than −20 kJ/mol, indicating a spontaneous and physical adsorption process. UV–Vis and FTIR investigations showed the formation of protective layer on mild steel surface. Statistical analysis is used to correlate the corrosion rate as a function of PAM concentration and temperature. Quantum chemical studies are used as a powerful tool for microscale analysis.