Improvement of Oxidation Resistance of Mild Steel by SiO2-Al2O3 Sol Gel Coating

Abstract

SiO2-Al2O3 sol gel coating solution was used for coating of mild steel substrate by dip coating technique with withdrawing speeds of 250, 500, 750 and 1000 mm/min. The coatings were subsequently heat treated at 200 degrees C for 1 hour in order to improve their corrosion resistance properties. The coating sol was synthesised using Glycidoxypropyltrimethoxysilane (C9H20O5Si) and Aluminium triisopropylate (C9H21O3Al). The corrosion resistance of the both coated and uncoated samples was evaluated by the Tafel polarization in NaCl solution. Fourier transformed infrared (FTIR) and energy dispersive spectroscopy (EDS) analyses were used to identify the presence of various functional groups in the coating solution. A comparison of the corrosion resistance of the coated and uncoated mild steel is presented. Variation of corrosion potential (E-corr) has increased and corrosion current density (i(corr)) has decreased in the coated samples. i(corr) values of coated specimens, heat treated at 200 degrees C, were 12 to 14 times smaller than those of uncoated specimen. The measured electrochemical parameters indicate that the corrosion resistance was improved by the coating.