exerted by the exposition to atmospheric agents in conformity with standards astm g53 d 4329 sae j2020 and iso 4892 the results of the measurements are graphically illustrated in fig3 in which the mean lifetime expressed in hours of the lenses of example 2 are compared with the lifetimes of other lenses in the aforementioned fig3 the bars labeled blue bronze black and silver refer to polycarbonate lenses provided with a cr and sio based two layered coatings as it can be noted from the histogram reported in fig3 the coating of the invention has significantly improved adhesion properties with respect to those of the two layered coatings of known type for the purpose of evaluating the abrasion resistance of the coating according to the previous example 2 with respect to that of two layered coatings of known type another comparative test was carried out u2014 known in the field by the name of u201c steel wool test u201d such a test is carried out by rubbing steel wool on the surface of the lens the damage caused by the abrasion is evaluated in terms of increase of scratches on the lens the steel wool test was carried out using a modified sutherland ink rub tester james river corp u2014 kalamazoo mich u s a wherein the rubber pad was replaced by a flake of standard steel wool grade 000 the steel wool flake was subject to a 2 kg weight placed in oscillation for a predetermined number of abrasion cycles the lenses were examined with a microscope.