Inhibition of Mild Steel Corrosion in Acidic Medium Using Starch and Surfactants Additives

The corrosion inhibition of mild steel in 0.1M H2SO4 in presence of starch (polysaccharide) was studied using weight loss and potentiodynamic polarization measurements in the temperature range of 30-60 degrees C. Starch inhibits the corrosion rates of mild steel to a considerable extent; the maximum inhibition efficiency (%IE) being 66.21% at 30 degrees C in presence of starch concentration of 200 ppm. The effect of the addition of very small concentration of sodium dodecyl sulfate and cetyl trimethyl ammonium bromide on the corrosion inhibition behavior of starch was also studied. The IE of starch significantly improved in presence of both the surfactants. The effect of surfactants on the corrosion inhibition behavior of starch appears to be synergistic in nature. Starch alone and in combination with surfactants is found to obey Langmuir adsorption isotherm from the fit of the experimental data of all concentration and temperature studied. Phenomenon of physical adsorption is proposed from the trend of IE with temperature and also the values E-a, Delta G(ads), and Q(ads) obtained. The results obtained by potentiodynamic polarization measurements are consistent with the results of the weight loss measurement. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1558-1565, 2011