Inhibition Effect of Cassava Starch−Acrylamide Graft Copolymer on Aluminium in KOH Solution

Graft copolymerization of natural cassava starch with acrylamide was used to prepare cassava starch-acrylamide graft copolymer. Weight loss, potentiodynamic polarization curve, scanning electron microscopeand atomic force microscope methods were used to study the inhibitory effect of scanning electron microscope on aluminum in 0.5 mol/L KOH solution. The results show that the corrosion rate of aluminum is significantly decreased after adding cassava starch-acrylamide graft copolymer to KOH solution, indicating that cassava starch-acrylamide graft copolymer is a good inhibitor. Inhibition efficiency increases with the increase of the inhibitor dose, but decreases with the increase of temperature. The maximum inhibition efficiency of 1.0 g/L cassava starch-acrylamide graft copolymer at 20 ℃ is 55%, but dropped to only 17% at 50 ℃. Inhibition performane enhances with the increase of immersion time, and reaches optimum at 6 h, thus showing better inhibitive stability. The adsorption of cassava starch-acrylamide graft copolymer on the aluminum surface conforms to Langmuir adsorption isotherm with the standard Gibbs adsorption free energy of −225.58 kJ/mol, and the adsorption mechanism is the complex adsorption in which physisorption and chemisorption occur simultaneously. Polarization curves shows that cassava starch-acrylamide graft copolymer is a mixed inhibitor type corrosion inhibitor, and the maximum positive shift is only 16 mV. Both scanning electron microscope and atomic force microscope test results show that the degree of corrosion and surface roughness of are significantly dropped for the alumiunium immersed in KOH solution containing cassava starch-acrylamide graft copolymer.