The present invention relates to a method of inhibiting corrosion experienced during use of a base oil or lubricant by the addition of a polyester corrosion inhibitor. More especially, the polyester corrosion inhibitor is the reaction product of an alk(en)yl substituted succinic anhydride wherein the average number of succinic groups per alk(en)yl group is less than 3.0, and at least one polyol. There is also provided a composition comprising such a polyester corrosion inhibitor and use of such a composition as a corrosion inhibitor, as well as a base oil or lubricant comprising such a polyester corrosion inhibitor.