Analytical and electrochemical study of structure and properties of hybrid Na montmorillonite-silica coatings for corrosion protection

Analytical and electrochemical study of structure and properties of hybrid Na montmorillonite-silica coatings for corrosion protection

The study deals with the investigation of a sol–gel/nanoclay composite coating as a protective layer for the corrosion protection of hot dip galvanized (HDG) steel. Sol–gel coatings prepared from glycidoxypropyltrimethoxysilane, tetraethoxysilane and methyltriethoxysilane with 2 wt.% of sodium montmorillonite were investigated. The effect of different curing times (2, 5, 10, 15 min) and different curing temperatures (90 °C, 150 °C, 180 °C) on the protection properties of the hybrid layer was investigated. Fourier Transform Infrared Spectroscopy (FT-IR) measurements highlighted that the higher is the curing temperature, the higher is the densification of the sol–gel network. FT-IR spectroscopy measurements underlined that the Si\O\Si/Si\OH ratio rises by increasing curing time or temperature. The densification of the network through formation of siloxane bonds was found to be responsible for the improved protection offered by the sol–gel layer studied using electrochemical techniques as Electrochemical Impedance Spectroscopy (EIS) and polarization curves)