Electrochemical performance of sol-gel derived phospho-silicate-methacrylate hybrid coatings
The sol–gel derived hybrid coatings containing three different compositions of methacrylate-phospho-silicate on mild steel substrates were characterized using potentiodynamic polarization, Electrochemical Impedance Spectroscopy (EIS) and Scanning Kelvin Probe (SKP). The corrosion current and potential along with the polarization resistance were determined using potentiodynamic measurements. The surface work function measured using SKP is correlated to the corrosion potential through a linear equation. The protection of the substrate is rendered by the strong interfacial interaction through acid–base interaction of P–O− group from phosphate with Mn+ from metallic substrate. Also, the coatings are intact and form a highly barrier layer, which restricts the permeation of electrolyte to the substrate surface. Among the studied hybrid coatings, M:E – 3:7 coated samples show better protection through strong interfacial interaction in combination with the defect-free, intact coating.