Common polyols used in alkyd resin production include glycerol, pentaerythritol, and trimethylolpropane. Frequently used dibasic acids include phthalic anhydride (commonly referred to as phthalic acid) and isophthalic acid. Alkyd resin coatings are known for their good weather resistance, excellent adhesion, high gloss, and full-bodied finish, and they are also easy to apply. However, the resulting paint film is relatively soft and exhibits limited resistance to water and alkalis. Alkyd resins can be combined with other resins to formulate various types of self-drying or oven-drying enamels, primers, topcoats, and clear varnishes with diverse performance characteristics. They are widely used in the coating of bridges and other structures, as well as machinery, vehicles, ships, aircraft, and instruments.