Case Studies

Interstate Bridge

AZZ Bridge and Highway Interstate Bridge

No corrosion maintenance for 41 years and counting.


Structure: Castleton Bridge - north bound lanes galvanized steel, south bound lanes painted steel.

Completed: 1970

Location: Castleton exit of interstate 69 in Hamilton County, Indiana (snow belt)

Owner: Indiana Department of Highways

Environment: This is a suburban bridge with high traffic volume passing over and under.  De-icing solutions and salts have been applied regularly over the years.

Maintenance: North bound lanes (galvanized steel beams) have had no corrosion related maintenance since construction.  South bond lanes (painted steel beams) were repainted in 1984 and zinc metalized in 2002.

The north bound lanes were last inspected in September, 2011 in accordance with ASTM A896/A896M-09 "Standard Practice for Conducting Case Studies on Galvanized Structures."  All coating thickness measurements still meet or exceed ASTM specifications for new galvanizing.  Even with cruel winters, heavy salting and pigeon droppings, this bridge is expected to remain corrosion maintenance free for many years to come.  Hot dip galvanizing continues to be the most cost effective, hassle free corrosion protection system available for structural steel bridges across America.