A hardener composition for use as a component of a two component
polyurethane coating composition, comprising a polyisocyanate, a catalyst
for promoting reaction of the polyisocyanate with a reactive hydrogen
compound, and one or more antioxidants selected from: a first antioxidant
comprising one or more of sterically hindered phenol antioxidants and
secondary aryl amine antioxidants, and a second antioxidant comprising
one or more organophosphite antioxidant, exhibits improved color
stability.