Protection of 6061 Al-15%_(v) SiC_(P) composite from corrosion by a biopolymer and surface morphology studies

The protective action of biopolymer starch on 6061 Al-15%_(v) SiC_(P) composite in 0.25 M hydrochloric acid was studied by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques with temperature ranging from 303 to 323 K. The concentrations of starch used were in the range of 0.1 to 0.8 g L^–1. The surface morphology studies were carried out using Scanning Electron Microscope, Energy Dispersive X-ray analysis, Atomic Force Microscope and X-ray Diffraction analysis techniques. Suitable mechanism was proposed for the corrosion and inhibition process. Results indicated increase in the efficiency of the inhibitor with its increase in the concentration and with temperature. Maximum inhibition efficiency of 84% was observed at 323 K for 0.8 g L^–1. Starch acted as a mixed inhibitor. Kinetic and thermodynamic studies showed that starch underwent chemical adsorption and obeyed Langmuir adsorption isotherm. Surface morphology studies confirmed the adsorption of inhibitor on the surface of metal matrix composite. Results obtained by potentiodynamic polarization method and electrochemical impedance spectroscopy method were in good agreement with one another.