Corrosion-resistant sol-gel coatings

Corrosion of iron or steel (anodic reaction Fe — Fe + 2e and cathodic reaction 4Fe + O2 + tOH20 4Fe(OH)3 + 8H+) leads to formation of surface hydroxides. The main constituents of oxides formed during atmospheric corrosion of steels are y-FeOOH (lepidocrocite), a-FeOOH (goethite), y5-FeOOH (akaganite) and -FeOOH (feroxyhite). These hydroxyl groups in rast have a tendency to react with hydroxyl groups of hydrolyzed metal alkoxide from sol-gel coatings. 

When an alrrminitm sitrface is exposed to the atmosphere, it forms a natural white coloured oxide (Al(OH)3) film, which is responsible for its corrosion resistance. Although this oxide film makes the alrrminitm surface stainless, it cannot protect the aluminum substrate imder severe corrosion conditions, and therefore aluminum 

6 Silane based coating interaction with aluminum and magnesium. 

Liu et al. prepared a TEOS modified sol-gel coating nsing vinyltrimethoxy-silane (VMS), 3-(methacryloxy)propyltrimethoxy silane (MPMS) and 

Pathak et at. developed hexamethoxymethylmelamirte (HMMM) and amirtosilane ctrred GPTMS and methyltrimethoj silane (MTMS) based 

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