CORROSION PREVENTING COVERING

摘要

A corrosion preventing factory or field applied coating has at least two discrete organic polymeric layers directly or indirectly united together. A first of said layers has a water vapour permeability of 0.005 to 10 g.mm/m2/24h at 23 ~C, 100 % RH. A second of said layers has an oxygen permeability of 0.01 to 10 cm3.mm/m2/24h.atm at 23 ~C, 50 % RH, and/or a carbon dioxide permeability of 0.01 to 30 cm3.mm/m2/24h.atm at 23 ~C, 50 % RH. In aggregate the coating has a water vapour transmission rate of 0.05 to 0.6g/m2/24h at 23 ~C, an oxygen transmission rate of 0.01 to 10 cm3/m2/24h.atm at 23 ~C and/or a carbon dioxide transmission rate of 0.01 to 20 cm3/m2/24h.atm at 23 ~C. These coatings can serve to greatly retard corrosion and in the case of the carbon dioxide barrier material greatly reduces stress corrosion cracking.