Hydrophobic coating is a multi-purpose, water-repellent coating. Many people use hydrophobic coating as a sealant for bikes, boats, automobiles, and more to protect paint jobs and prolong the lifespan of the paint. Most hydrophobic coatings have a material mixture known as fluorinated polyurethane elastomer. Applying a hydrophobic coating to a surface, such as an automobile, helps repel fog and moisture. This makes it easier to see when you are driving while providing paint protection and rust prevention. These coatings usually last about one year before you need to reapply.