Corrosion Protection and Self-Healing by Sol-Gel Process: A Review of Recent Patent Literature

Aluminum alloys and magnesium alloys are widely used due to their light weight properties and being inexpensive for application in automobiles, aircrafts, household articles and industries etc. These materials are useful because of their physical characteristics, such as stiffness and high strength-to-weight ratio. Mild steels are also used in structural applications due to their intrinsic hardness property. However, they all are highly susceptible to corrosion in aggressive saline environments. Many research groups have been working on various methods of protecting them from corrosion by producing either a barrier coating, barrier cum self healing coating or an inhibitor coating. Among all the coating deposition techniques, hybrid sol-gel coatings are attractive from the point of view of being amenable to scale-up in addition to introducing multi-functionalities (barrier cum self-healing, easy-to-clean, anti-bacterial) in the coating. In this paper, recent patents on corrosion protection and self-healing coatings produced by sol-gel method for Aluminum alloys, Magnesium alloys and Mild steel are reviewed.