Polyurethane coatings are another group which, like the epoxies, can
have a number of coating combinations which create different properties.
Polyurethane coatings contain resins made by the reaction of isocyanates with
hydroxyl- containing compounds, e.g. water, mono- and diglycerides made by the
alcoholysis of drying oils, polyesters, polyethers, epoxy resins, acrylics.
As a matter of fact, wherever there is an active hydroxyl group, the isocyanate
will react with it.
Urethane coatings have excellent impact properties and can withstand both
direct and reverse impact, which is a property that many other resistant
coatings do not have.
The same urethane coating can be designed to have flexibility, impact
resistance, and high abrasion resistance, all combined into one coating.
Generally, urethane coating are used as topcoats and applied over good epoxy
primers for best results for corrosion condition.