Improvement of corrosion resistance of AA6061 alloy by tapioca starch in seawater

This study examines the use of tapioca starch for improvement of corrosion resistance of AA6061 alloy in seawater. Gravimetric, potentiodynamic polarization, linear polarization resistance and electrochemical impedance measurements were employed to study the corrosion behavior of AA6061 alloy in seawater. The electrochemical measurements for AA6061 alloy in seawater showed that the presence of tapioca starch significantly decreases the corrosion rates, corrosion current densities (i(corr)), and double layer capacitance (C-d1), simultaneously increases the values of polarization resistance (R-p). The inhibition efficiencies increase with increasing of tapioca starch concentration. The Langmuir adsorption isotherm fits well with the experimental data. The nature of adsorption of tapioca starch on the metal surface has also been examined. The analysis of SEM and EDS confirmed the formation of precipitates of tapioca starch oil the metal surface, which reduced the overall corrosion reaction. (C) 2009 Elsevier B.V. Ail rights reserved.