Department of Chimical Engineering

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The use of organic or inorganic coatings for protecting metallic substrates is widely accepted in various structural engineering applications, such as aerospace, automobiles. In order to meet the industry requirements, the ability to achieve good corrosion resistance properties under a wide variety of conditions should be considered. The present work is based upon the use of Mg-Al sol-gel material to protect mild steel substrates against NaCl media. Filiform corrosion was employed in this experimental work to identify the possibility of corrosion on mild steel substrates compared with the commercial epoxy resin. Filiform corrosion is usually initiated by weak points or discontinuities in the film they never cross each other, and their growth is independent of light and of the metallurgical structure of the metal substrate and the driving force of this type of corrosion is controlled by the osmotic action (pressure) in the growing corrosion cell. The attack of this type of corrosion is usually affects steel. Visual examination of mild steel samples for both coated system showed the unstable adhesion property of epoxy resin on mild steel surface compared with that in the sample coated with sol-gel material. This can be attributed to chemical structure of Mg-Al sol-gel material play a key role in this behavior. IR spectra showed the two small bands at 3072 and 3049 cm-1 correspond to the C-H stretching vibrational bands. Additional a very strong bands between 1300 and 1200 cm-1 proves the presence of magnesium into the structure of the sol-gel materials. Also, the combination bands at 1711 and 1630 cm-1 are visible in these spectra and are related to the incorporation of aluminum and magnesium into the sol-gel structure. All these chemical bonds within the structure of sol-gel play a role in reducing the inter of water molecules within the Mg-Al\sol-gel and develop more adhesion bonding at the interface of sol-gel material and metal surface.