... crescent, sand, double-plane and flat surface gratings:1, corrosion resistance With excellent corrosion resistance to gas and liquid media of acids, alkalis ... strength density of FRP gratings is not above 2,only 1/4 of that of steel,2/3 of that of ... index is not lower than 28(GB 8924).4, Aging resistance Using time is over 50 years. 5, safe the products ...