When hot-dip galvanized steel is painted, the duplex system provides a more sophisticated manner of corrosion protection. The galvanized coating protects the base steel by providing both cathodic and barrier protection. The paint coating acts as a barrier protection for the hot-dip galvanized coating and significantly reduces the corrosion rate of the zinc.
The increased lifetime that can be provided with a combination of paint over galvanized steel makes this type of corrosion protection system very attractive for structures designed to last a long time in aggressive atmospheres.
Aluzinc is cold rolled galvanized steel with metal coating composed of Aluminum (55%), Zinc (43.4%) and Silicon (1.6%). It is formable, weldable and readily accepts paint finishes. Aluzinc coated steel has superior long-term corrosion resistance in most atmospheric conditions. This is achieved through the combination of the sacrificial protection of the zinc and the barrier protection of the aluminum.