Influence of the Cerium Concentration on the Corrosion Performance of Ce-doped Silica Hybrid Coatings on Hot Dip Galvanized Steel Substrates

摘要

The aim of this work was to investigate the effect of the cerium concentration on the morphology andanticorrosion performance of ceriumilane hybrid coatings on hot dip galvanized (HDG) steelsubstrates. 3-glycidoxypropyltrimethoxysilane (GPTMS) and bisphenol A (BPA) were employed asprecursors to prepare the solel based silane coating. Cerium nitrate hexahydrate was added to thesilane coatings as dopant in five different concentrations. The morphology of the coatings before andafter the corrosion test was examined by scanning electron microscopy (SEM), indicating an effect ofthe cerium concentration. Very low and very high cerium concentrations deteriorate the corrosioninhibition in the sol-gel matrix and consequently, there is an optimum concentration of cerium nitrate.Accelerated salt spray testing showed that corrosion near an artificial scratch is blocked efficiently byhigh cerium nitrate contents, whereas uniform corrosion is inhibited effectively with comparativelylow ceria contents. Electrochemical studies indicate a general beneficial effect of the incorporation ofcerium nitrate, although the performance of the coated substrate depends on the cerium nitrate content.The results of electrochemical impedance spectroscopy (EIS) and electrochemical polarizationconfirmed that the corrosion resistance of the coatings initially increases and then decreases as thecerium concentration goes up. Optimal corrosion resistance was obtained at a cerium concentration of0.05 M.