Who hasn’t noticed the rust on the Park Ave and Main Street bridges?  New bridge parts are less subject to rusting because they are made from galvanized steel (an iron-zinc alloy) which prevents oxygen and water from reaching the steel and slows corrosion. All new structural bridge parts must be made of steel manufactured in the United States.  These new galvanized steel bolts for the Main Street bridge are samples from different lots.   A sample from every lot is tested for strength.  Putting the Main Street bridge back together will require several thousand bolts.