Electrochemical corrosion behaviour of silica hybrid sol-gel coatings


The aim of the present work is to produce hybrid inorganic-organic nanostructured sol-gel coatings and to study their structure and corrosion resistance. The coatings were synthesized by sol-gel technology at room temperature using vinyltrimethoxysilane (VTMS) as silicon precursor and methylmethacrylate (MMA) or hydroxyethytmethacrylate (HEMA) as organic materials in different proportions. The coatings were deposited on mill steel substrates and thermally treated at 25 and 200 degrees C. The composition and the structure of the hybrids were characterized by FTIRS, XRD, BET-analysis, EDS, SEM and AFM. The presence of strong chemical bonds (Si-C, Si-O-C, Si-CH3) between inorganic and organic parts of the hybrid materials, which are in amorphous state was proved. The size of nanounits and their aggregates as well as the surface roughness of the samples were also determined. The corrosion resistance of the coatings was studied using electrochemical potential-sweep technique and a model corrosive medium of 0.5 M Na2SO4 solution. It has been shown that the coating affects both partial corrosion reactions, but it decreases more strongly the anodic metal dissolution, thus decreasing the corrosion rate of the steel substrate more than an order of magnitude. The presence of a chemical bond of the coating with iron from the substrate is also established, which is in accordance with the good adhesion of this type of coating. The results of the present study suggest a possible application of the obtained hybrid materials as transparent coatings with good protective properties.






Raicheff, RG; Chernev, GE; Zaprianova, VG; Ivanova, DI; Djambaski, PR; Samuneva, BI; Salvado, IMM

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