Information courtesy of the American Galvanizers Association - c. 2000
Readily Available
With the availability of ever expanding kettle sizes, finding local facilities to hot-dip galvanize larger beams, trusses and girders for new bridges is as easy as ever. For many years galvanizing has been the corrosion protection mechanism of choice for short-span bridge designers and owners. The existence of longer, wider and deeper galvanizing capacity gives public authorities an easy choice for maintenance-free galvanized bridges that withstand the attack of corrosive elements.
Corrosion Protection
Zinc protects steel from corrosion. The reason for the extensive use of hot-dip galvanizing is the two-fold protective nature of the zinc coating. As a barrier coating, it provides a tough, metallurgically bonded zinc coating that completely covers the steel surface, isolating it from the corrosive action of the environment. Additionally, zinc's sacrificial action protects the steel even where damage produces minor discontinuities in the coating.
Low Maintenance
Documented 30-year plus maintenance-free lives of galvanized steel bridges attest to the effective corrosion protection provided by hot-dip galvanizing. The long life provided by hot-dip galvanizing makes precious maintenance dollars available for other projects.
Financial Considerations
Compared to many paint systems, the initial cost of hot-dip galvanizing is less. Life-cycle cost analyses make hot-dip galvanizing the smart choice because galvanized steel may need no maintenance for 30 - 50 years. With a predictable long life expectancy, and little or no maintenance, the corrosion protection provided by hot-dip galvanizing can be capitalized over the entire life of the project, as opposed to being considered an annual operating expense.
Environmental
Galvanized bridges are environmentally friendly. Zinc is a naturally occurring metal that is essential for life. Zinc is a part of the dietary RDA, is used for a variety of medicinal purposes and contains no volatile organic compounds. Additionally, galvanized steel is virtually 100% recyclable.
Design
Hot-dip galvanizing does not change the structural integrity of the steel. Galvanized fasteners, hardware and auxiliary steel are readily available. Faying surfaces may require some roughing.
Reinforcing Steel
Hot-dip galvanized reinforcing steel has been in use for over 30 years in bridge decks and has proven to be an outstanding corrosion protection system even in aggressive locations, including high road salt areas, and ocean marine environments. Required overlap lengths for galvanized rebar are less than for epoxy coated bars and lead to substantial cost savings. No special handling or storage requirements, a durable coating requiring no touch-up and repair, and fabrication after coating make galvanized rebar the choice of contractors.
Click here to view - Zinc Coatings: Microstructures of Various Zinc Coatings (pdf format), Copyright 2000, American Galvanizers Association.