Preparation of hybrid silica sol–gel coatings on mild steel surfaces and evaluation of their corrosion resistance

Abstract

• Hybrid silica coatings were prepared on mild steel by dip coating technique. • The i corr values of the coating specimens were smaller than uncoated specimen. • The coating film was noted to be between 1.8 and 2 μm thick. • Aminopropylethoxysilane coated specimen has shown maximum R cor . Hybrid silica sol–gel coatings were prepared on mild steel substrate by dip coating technique. The coatings were subsequently heat treated at 200 °C in order to improve their corrosion properties. The coating sols were synthesized using Glycidoxypropyltrimethoxysilane (glymo) and Aminopropylethoxysilane (ameo) as precursor materials. Potentiodynamic polarization curves were derived and Electrochemical Impedance Spectroscopy (EIS) measurements were made in NaCl solution. The surface and cross-section morphology of coated specimens were characterized by scanning electron microscopy (SEM). Fourier transformed infrared (FTIR) analysis was used to identify the presence of various functional groups in the coating solutions. A comparison of the corrosion resistance of the coated and uncoated mild steel was presented. The results indicated that the corrosion resistance of the coated mild steel was improved considerably.