Cassava starch graft copolymer as a novel inhibitor for the corrosion of aluminium in HNO ₃ solution

Cassava starch graft copolymer (CSGC) was prepared by grafting acryl amide (AA) onto cassava starch (CS). The inhibition effect of CSGC on the corrosion of aluminium in HNO 3 solution was studied by weight loss, electrochemical techniques, scanning electron microscope (SEM), atomic force microscope (AFM), contact angle images and X-ray photoelectron spectroscopy (XPS). Quantum chemical calculation and molecular dynamic simulation were performed to theoretically investigate the adsorption mechanism. CSGC is an effective novel inhibitor, and shows higher inhibition efficiency than either CS or AA. The adsorption of CSGC on aluminium surface obeys Langmuir isotherm. CSGC is a mixed-type inhibitor, while mainly retards the anodic corrosion. EIS consists of a large capacitive loop at high frequencies followed by a small inductive one at middle frequencies and the second capacitive loop at low frequency values, and the impedance strengthens with the concentration of CSGC. SEM and AFM confirms the corrosion of aluminium surface is prominently retarded after adding CSGC to the media. Contact angle image suggests that the inhibited aluminium surface is of hydrophobic nature. XPS provides the evidence of the adsorptive inhibitor of CSGC on aluminium surface. Quantum chemical calculation and molecular dynamic simulation can be well theoretically elucidate that CSGC shows higher adsorption and inhibition ability than CS.