Corrosion inhibition of galvanized steel in hydrochloric acid medium by a physically modified starch

Native starch extracted from sweet potato tubers was modified via extrusion. The native starch and modified starch were characterized by Fourier transform infrared (FTIR) spectroscopy, which revealed slight modifications in peak position and intensities on starch modification. The modified starch was evaluated as a corrosion inhibitor of galvanized steel in 1 M HCl solution by gravimetric and potentiodynamic polarization measurement techniques. Results obtained from gravimetric measurement reveals that the modified starch inhibition efficacy was dependent on time, concentration and temperature, increasing with increase in concentration and decreasing with increase in time of immersion and temperature of the system. Maximum inhibition efficiency of 64.26% was obtained at a concentration of 0.7 g/L PMS. Also, result from polarization technique indicated that the modified starch belonged to a mixed-type inhibitor. Adsorption of the inhibitor on the galvanized steel surface was found to obey the Langmuir adsorption isotherm.