To counteract the corrosion of steel bridges and extend their life beyond 100 years, the Norwegian state body that manages the roads (NPRA) he prescribed, its valley 1967, the use of TSZ-Duplex (Thermal galvanizing plus paints) which system is more effective and economical.
The first applications date back to 1964 and concern the Bridge wreck which has been protected with a coating of 100 microns of zinc, on which two layers of alkyd-based paints were deposited 100 microns each.
In the 2012, after 48 years of service, The first preventive maintenance in the form of a wash and the application of a new coat of paint was carried out, given the perfect state of the Zinc below.
The combination TSZ-Duplex creates a synergistic reaction with a double benefit: on one side extends from 1,5 a 2,5 times the duration corresponding to the sum of the two single coatings and on the other hand avoids subfilm corrosion when the paint is cracked or damaged, because the underlying zinc continues the protection of the steel by acting as an anode.