Enhanced corrosion inhibition properties of carboxymethyl hydroxypropyl chitosan for mild steel in 1.0 M HCl solution

Synthesized carboxymethyl hydroxypropyl chitosan (CHPCS) containing both carboxymethyl and hydroxypropyl groups was investigated as a corrosion inhibitor for mild steel in 1.0 M HCl solution using weight loss, open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. It was found that the compound behaved like a mixed-typed corrosion inhibitor that simultaneously inhibited the anodic dissolution and hydrogen evolution reactions. The compound inhibited corrosion at a low concentration and reached an inhibition efficiency of 95.3% in 1000 ppm (by weight). It was also found that the equivalent circuit model of one time constant was used during EIS analysis. The absorption of CHPCS on the metallic surface obeyed the Langmuir isotherm with a negative value of the free energy of adsorption G . Scanning electron microscopy (SEM) was carried out to corroborate the test results. The potential of zero charge revealed that the corrosion inhibition mechanism involved physisorption and chemisorption processes. CHPCS was synthesized and showed better corrosion inhibition than HPCS (corrosion inhibition of 95.3%); its corrosion inhibition mechanism is presented.