The use of duplex coating systems (hot dip galvanizing or thermal spray coating with one or more liquid-applied coatings) for long term protection of structural steel is becoming more mainstream in many industries. This paper describes the advantages of employing duplex coating systems as well as some important considerations for designers prior to specifying their use. It also highlights an ongoing initiative to help agencies more efficiently and effectively use duplex coatings on steel bridges by developing guidelines, standards, and other materials.
Extreme temperatures, rain, and freeze thaw cycles can all attack structures causing corrosion and therefore high maintenance costs. The UK DOT ensures maintenance is kept to a minimum by protecting its bridge stock using an effective waterproof coating which meets the exacting standards specified in BD47. A number of polyurethane based waterproofing systems have now met this standard. The inherent properties, ease of installation and long-term protection offered by polyurethane systems make them extremely popular amongst client authorities across the world.