review on the sol-gel based coatings used for the protection of metal substrates against corrosion

Chemical treatment of the metal substrates prior coating application is an effective way of improving the adhesion and corrosion protection properties of the organic coatings. Conversion coatings i.e. chromate and phosphate have been widely used for this purpose and improved the organic coating adhesion and corrosion protection properties significantly. However, the use of such coatings has been strictly restricted in recent years because of its high toxicity and environmental problems. Recently, sol-gel based coatings have been introduced as more environmental friendly alternative, less costly, high accessibility for equipment and easy to application on the metal substrates. In this study, the preparation procedures and application methods of the sol-gel based coatings as well as the main factors affecting theirs properties will be discussed. Also, the constraints and prospects of this area of research will be discussed.