Oil-Based Coatings

Oil-Based Coatings

Oil-based paints (oil paints) are the oldest organic coating materials. The content of Oil paints is natural drying oils such as linseed oil, tung oil, and soybean oil which will undergo autoxidative polymerization in the presence of catalytic driers and atmospheric oxygen. The catalytic driers are metallic soaps such as cobalt, lead, and manganese naphthenates or octoates.

During curing of paint, the atmospheric oxygen reacts with the oil to form hydroperoxides which will decompose into radicals and then initiate polymerization of the binder. The drier will catalyze the formation and decomposition of the hydroperoxides and thereby accelerate film formation.

The thickness of film will influence the curing process. If the film is too thick, the oxygen will penetrates the film very slowly and the inside of paint will remain soft. The thickness of paint ussually 25-30 micron on vertical and 40-50 micron on horizontal surfaces. The drying time is depent on the room temperature, higher temperature will increase the speed of drying.
Oil-based paints are tough but not excessively hard. It has limited weather resistance. It will lose its gloss and tend to yellow much more than otehr binders (ca. two years).
The use of oil paint has decrease and have been replaced by other types of binder. Its renewable natural oil are environment friendly as long as toxic pigment and solvent are not used.